A work vehicle equipped with an HST traveling drive device, includes: an operation quantity detector that detects an operation quantity representing an extent to which an accelerator pedal is operated; a rotation rate detector that detects an actual rotation rate at a prime mover; a requested rotation rate calculation unit that calculates a requested rotation rate for the prime mover based upon the operation quantity detected by the operation quantity detector; and a prime mover control unit that controls the actual rotation rate based upon the requested rotation rate calculated by the requested rotation rate calculation unit. When the requested rotation rate is higher than a predetermined value, the requested rotation rate calculation unit calculates a rate of acceleration for the requested rotation rate based upon a difference between the requested and the actual rotation rate detected by the rotation rate detector and calculates the requested rotation rate based upon the calculated rate of acceleration.