An engine control device of the wheel loader includes a travelling state detecting unit for detecting a travelling state of the wheel loader, a mode switching determining unit, an acceleration speed detecting unit and a switching time controlling unit. The acceleration speed detecting unit detects the acceleration speed of the wheel loader when the mode switching determining unit determines that it is required to switch between the engine output modes from a low output mode to a high output mode based on a detection result of the travelling state detecting unit. The switching time control unit controls the switching time from start to end of mode switching to be: a first time when the acceleration speed detected by the acceleration speed detecting unit is either 0 or negative; and a second time greater than the first time when the detected acceleration speed is positive.