A robot mechanism is provided, including a base, a main body, a motor, a driver, a bottom plate, a flexible heat conductive member, and a controller. The main body is connected to the base and has a housing. The motor and the driver are disposed in the main body, and the driver is electrically connected to the motor. The bottom plate is disposed on the housing and situated between the driver and the housing, and a gap is formed between the bottom plate and the driver. The flexible heat conductive member is disposed between the driver and the housing. The flexible heat conductive member contacts the driver. The controller is detachably disposed in the base.