A speed change auxiliary device of a lathe is provided. A side chamber of the lathe is provided with a shaft seat and a bottom shaft seat at the top and bottom thereof. An auxiliary device is provided between the shaft seat and the bottom shaft seat. The auxiliary device includes a shaft. A spring, an eccentric block, an engaging member, a positioning nut, a rotary sleeve and a fixing block are fitted on the shaft. The rotary sleeve includes a handle. Two sides of an inner circumferential surface of the rotary sleeve have protrusions. The protrusions each have an upright surface and an upper guide bevel at two sides thereof. The fixing block is disposed on the bottom shaft seat. Two sides of a circumferential surface of the fixing block have recesses. The recesses each have a stop surface and a lower guide bevel at two sides thereof.

A speed change auxiliary device of a lathe is provided. A side chamber of the lathe is provided with a shaft seat and a bottom shaft seat at the top and bottom thereof. An auxiliary device is provided between the shaft seat and the bottom shaft seat. The auxiliary device includes a shaft. A spring, an eccentric block, an engaging member, a positioning nut, a rotary sleeve and a fixing block are fitted on the shaft. The rotary sleeve includes a handle. Two sides of an inner circumferential surface of the rotary sleeve have protrusions. The protrusions each have an upright surface and an upper guide bevel at two sides thereof. The fixing block is disposed on the bottom shaft seat. Two sides of a circumferential surface of the fixing block have recesses. The recesses each have a stop surface and a lower guide bevel at two sides thereof.