[Problem] To provide a power transmission device capable of, when changing gears, reaching a target point more rapidly than conventionally possible. [Solution] A power transmission device comprising a main drive source, a continuously variable transmission, and a control unit. The continuously variable transmission comprises: a lever crank mechanism that converts rotary motion of an input unit to pivoting motion of a pivot link; and an output shaft. A one-way clutch is provided on the output shaft. The output shafts rotates in one direction only, as result of the pivoting motion of the pivot link. The control unit increases (STEP 25) the drive force of the main drive source if a determination has been made (YES in STEP 23) that a force has been applied to a rotation radius adjustment mechanism, said force being in the reduced radius direction in which the rotation radius is reduced by the reduced radius force determination unit.