To provide a power transmission device for a vehicle that prevents a transmission belt from slipping even when a deceleration economy running is performed.

The power transmission device 10 for the vehicle includes: a first shaft 36 connected with an engine 12; a second shaft 50 connected with a drive wheel 24; a primary pulley 52 and a secondary pulley 54 fixedly installed on the first shaft 36 and the second shaft 50; and the transmission belt 58 wound around respective V-grooves 56 of the pulleys 52 and 54. The device also includes a belt type continuously variable transmission 20 that controls hydraulic fluid, which is pressure-fed from a mechanical hydraulic pump 44 driven by the engine 12, thereby continuously varying a gear ratio. The device further includes a hydraulic-type power transmission shut-off mechanism 74 that is disposed between the second shaft 50 and the drive wheel 24, allows power transmission between the second shaft 50 and the drive wheel 24 when the hydraulic fluid from the mechanical hydraulic pump 44 acts, and prevents the power transmission when the hydraulic fluid does not act.