The present invention is a control device for a variable displacement hydraulic pump by which the absorption horsepower of the hydraulic pump increases with excellent responsiveness and ON/OFF operations of a cut-off control of the maximum pressure can be selected. To this end, a hydraulic pump (2), a slow return valve (25) and a switching valve (24) placed parallel to each other in a flow path connecting a servo piston (4) and a servo valve (5); a solenoid valve (26), for controlling the pilot pressure of the switching valve (24); and an ON/OFF operation selectable selector (30), connected to a control device (10), are included; and the controlling device (10) outputs a command signal to the solenoid valve (26) when the selector (30) is switched ON to lower the operation speed of the swash plate angle of the hydraulic pump (2).