To install a larger battery without causing a longitudinal dimension to drastically increase, the present invention provides a direct drive unit designed such that a screw shaft (10) is rotatably arranged inside a unit body (1), an electric motor (20) and a battery (30) are arranged in parallel with the screw shaft (10), the electric motor (20) is driven using the battery (30) as a power source, and the screw shaft (10) is rotated by the electric motor (20), whereby a sliding member (14) threaded over the screw shaft (10) is moved along an axial center of the screw shaft (10), wherein a speed reduction mechanism (100) comprising planetary gear mechanisms (110, 120) is centered about the axial center of the screw shaft (10) in an area extending from a proximal end of the screw shaft (10), a second-step planetary carrier (124) of the speed reduction mechanism (100) is fitted to the end of the screw shaft (10), and a drive gear (23), a two-step intermediate gear (40), and a two-step input gear (50) are interposed between a first-step sun gear (111) of the speed reduction mechanism (100) and a drive shaft (22) of the electric motor (20).
