A golf ball according to the present invention includes: a module including an electronic circuit and its power source; a protective layer that surrounds an outer periphery of the module and is formed from a material having a Shore D hardness of at least 60; a core that surrounds an outer periphery of the protective layer; and a cover that surrounds an outer periphery of the core. A weight may be arranged on a surface of the protective layer. A difference between a value MOImax of the moment of inertia in a direction in which the moment of inertia of the golf ball is maximum and a value MOImin of the moment of inertia in a direction in which the moment of inertia of the golf ball is minimum is at most 1.0 g.Math.cm.sup.2.

A golf ball according to the present invention includes: a module including an electronic circuit and its power source; a protective layer that surrounds an outer periphery of the module and is formed from a material having a Shore D hardness of at least 60; a core that surrounds an outer periphery of the protective layer; and a cover that surrounds an outer periphery of the core. A weight may be arranged on a surface of the protective layer. A difference between a value MOImax of the moment of inertia in a direction in which the moment of inertia of the golf ball is maximum and a value MOImin of the moment of inertia in a direction in which the moment of inertia of the golf ball is minimum is at most 1.0 g.Math.cm.sup.2.

In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer and a cover of one or more layer, the inner core layer and outer core layer are each formed of a rubber composition made up primarily of a base rubber, the inner core layer has a diameter of not more than 30 mm; and the core has specific hardness ratios (JIS-C hardness/Shore D hardness) at specific points on the cross-section thereof. This golf ball has a reduced spin rate on full shots with a driver and middle irons, thus imparting to an excellent flight performance, and moreover has a good controllability in the short game on approach shots, making it ideal as a golf ball for professional golfers and mid- and high-level amateur golfers.

In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer and a cover of one or more layer, the inner core layer and outer core layer are each formed of a rubber composition made up primarily of a base rubber, the inner core layer has a diameter of not more than 30 mm; and the core has specific hardness ratios (JIS-C hardness/Shore D hardness) at specific points on the cross-section thereof. This golf ball has a reduced spin rate on full shots with a driver and middle irons, thus imparting to an excellent flight performance, and moreover has a good controllability in the short game on approach shots, making it ideal as a golf ball for professional golfers and mid- and high-level amateur golfers.

In a golf ball having a core, a cover and at least one intermediate layer formed therebetween, the core, intermediate layer and cover have respective specific gravities with a standard deviation of not more than 0.07 or less, the cover has a material hardness on the Shore D hardness scale of 52 or less, and the ball has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which is 2.8 mm or less. The amount of deviation in the ball center of gravity is exceedingly small, increasing the straightness with which the ball rolls on putts with a putter.