An automatic transmission apparatus is provided with a compact shifting mechanism. The apparatus includes an automatic transmission, the shifting mechanism arranged inside the vehicle cabin to have a shift lever to be manipulated by a driver and also adapted to allow a desired driving range of the vehicle to be selected by the driver's manipulating of the shift lever, a link mechanism to transmit a movement of the shift lever to the shifting mechanism and a manipulating-force assisting device acting on a connecting part between the shifting mechanism and the link mechanism to assist a driver's force to manipulate the shift lever, the manipulating-force assisting device having a motor as a driving source.