A work vehicle control device includes: a rotation speed control unit that controls an engine rotation speed in correspondence to an accelerator pedal operation quantity indicating an operating extent of an accelerator pedal; a speed ratio detection unit that detects a ratio of speed at an input shaft and at an output shaft of a torque converter, which is disposed between the engine and wheels; a decision-making unit that makes a decision that a fuel efficiency deteriorating condition exists if the torque converter speed ratio is less than a predetermined value or if the torque converter speed ratio is equal to or greater than the predetermined value and a target engine rotation speed corresponding to an operation of the accelerator pedal is greater than a preset value; and an informing unit that informs results of the decision made by the decision-making unit.