A work vehicle equipped with an HST traveling drive device, comprising: an operation quantity detector that detects an operation quantity representing an extent to which an accelerator pedal is operated; a rotation speed detector that detects an actual rotation speed at an engine; an indicated engine rotation speed setting unit that sets an indicated engine rotation speed for the engine based upon the operation quantity detected by the operation quantity detector; and a requested engine rotation speed calculation unit that calculates the requested engine rotation speed for the engine at each predetermined control cycle, characterized in that the work vehicle further comprises: a pedal operation decision-making unit that makes a decision whether the accelerator pedal is in a stepping on operation or in an easing off operation based upon the indicated engine rotation speed set by the indicated engine rotation speed setting unit and the requested engine rotation speed having been calculated at an immediately preceding control cycle; a condition decision-making unit that makes a decision whether raising or lowering a rate of acceleration of the requested engine rotation speed based upon a decision result made by the pedal operation decision-making unit, the requested engine rotation speed, and a difference between the requested engine rotation speed and the actual engine rotation speed; an acceleration/deceleration rate setting unit that sets a rate of acceleration or a rate of deceleration of the requested engine rotation speed, which is the rate of increase or the rate of decrease in the requested engine rotation speed per unit of time, based upon a decision result made by the condition decision-making unit; and an engine control unit that controls the actual engine rotation speed based upon the requested engine rotation speed calculated by the the requested engine rotation speed calculation unit, and the requested engine rotation speed calculation unit calculates a new requested engine rotation speed based upon the requested engine rotation speed having been calculated at the immediately preceding control cycle based upon the rate of acceleration or the rate of deceleration set by the acceleration/deceleration rate setting unit. an operation quantity detector that detects an operation quantity representing an extent to which an accelerator pedal is operated; a rotation speed detector that detects an actual rotation speed at an engine; an indicated engine rotation speed setting unit that sets an indicated engine rotation speed for the engine based upon the operation quantity detected by the operation quantity detector; and a requested engine rotation speed calculation unit that calculates the requested engine rotation speed for the engine at each predetermined control cycle, characterized in that the work vehicle further comprises: a pedal operation decision-making unit that makes a decision whether the accelerator pedal is in a stepping on operation or in an easing off operation based upon the indicated engine rotation speed set by the indicated engine rotation speed setting unit and the requested engine rotation speed having been calculated at an immediately preceding control cycle; a condition decision-making unit that makes a decision whether raising or lowering a rate of acceleration of the requested engine rotation speed based upon a decision result made by the pedal operation decision-making unit, the requested engine rotation speed, and a difference between the requested engine rotation speed and the actual engine rotation speed; an acceleration/deceleration rate setting unit that sets a rate of acceleration or a rate of deceleration of the requested engine rotation speed, which is the rate of increase or the rate of decrease in the requested engine rotation speed per unit of time, based upon a decision result made by the condition decision-making unit; and an engine control unit that controls the actual engine rotation speed based upon the requested engine rotation speed calculated by the the requested engine rotation speed calculation unit, and a pedal operation decision-making unit that makes a decision whether the accelerator pedal is in a stepping on operation or in an easing off operation based upon the indicated engine rotation speed set by the indicated engine rotation speed setting unit and the requested engine rotation speed having been calculated at an immediately preceding control cycle; a condition decision-making unit that makes a decision whether raising or lowering a rate of acceleration of the requested engine rotation speed based upon a decision result made by the pedal operation decision-making unit, the requested engine rotation speed, and a difference between the requested engine rotation speed and the actual engine rotation speed; an acceleration/deceleration rate setting unit that sets a rate of acceleration or a rate of deceleration of the requested engine rotation speed, which is the rate of increase or the rate of decrease in the requested engine rotation speed per unit of time, based upon a decision result made by the condition decision-making unit; and an engine control unit that controls the actual engine rotation speed based upon the requested engine rotation speed calculated by the the requested engine rotation speed calculation unit, and the requested engine rotation speed calculation unit calculates a new requested engine rotation speed based upon the requested engine rotation speed having been calculated at the immediately preceding control cycle based upon the rate of acceleration or the rate of deceleration set by the acceleration/deceleration rate setting unit.