A control apparatus for a tractor or wheel loader includes a speed change sensor that detects the step-on amount of a speed change pedal, an actuator that regulates a swash plate angle of a hydraulic pump based on the detection value of the speed change sensor, a transmission output unit rotation sensor that detects the revolution speed of an output shalt, and a control unit. When the speed change pedal is not stepped on, a braking force is applied to travel wheels and both of a forward drive clutch and a reverse drive clutch are disengaged. When a transmission drive output detected with the transmission output unit rotation sensor is not more than a fixed forward or reverse drive switching speed, either the forward drive clutch or the reverse drive clutch is engaged as the speed change pedal is stepped on.