An electric motor equipped with deceleration device (1) is provided with a main shaft component (200) that is formed substantially in a circular rod shape, and has one end portion (201) that is rotatably supported at a substantial center of a bottom portion (111) of a motor housing (110) and another end portion (202) that protrudes towards an outer side through an aperture in the motor housing (110), the main shaft component (200) is fixed to the motor housing (110) via the one end portion (201). An armature (130) is disposed inside the motor housing (110) so as to be on the same axis as the main shaft component (200) and so as to surround the main shaft component (200), and a deceleration device (10) is disposed between the armature (130) and the other end portion (202) of the main shaft component (200) so as to surround the main shaft component (200), and an output component (16), which is formed in a toroidal shape, is disposed on the same axis as the main shaft component (200) so as to surround the main shaft component (200).