An oscillator includes a resonator element provided with an excitation electrode, an oscillation circuit for oscillating the resonator element to generate an oscillation signal, a temperature sensor for generating a temperature signal for temperature compensation of the oscillation signal, a temperature control element for controlling temperature of the resonator element, and a container that houses the resonator element, the oscillation circuit, the temperature sensor, and the temperature control element, in which the temperature sensor and the temperature control element overlap the excitation electrode in plan view.

A crystal element having a first axis-second axis plane specified by a first axis derived from an X-axis and a second axis derived from a Z-axis as a principal surface and having a third axis derived from a Y-axis as a thickness direction. The first side surface of the first axis and the second side surface of the first axis are each constituted of a crystal face derived from the crystal and a plane that has a contour parallel to a normal line of the principal surface. The first side surface of the second axis and the second side surface of the second axis are each constituted of a crystal face derived from the crystal and a plane that has a contour parallel to a normal line of the principal surface, or constituted of a crystal face derived from the crystal non-parallel to the normal line of the principal surface.