A hydraulic controller comprising: a piston united with a valve; a cylinder accommodating the piston so that it can move longitudinally in the axial direction; a positive pressure chamber that is formed on one side across from the piston and into which pressurized oil flows for opening the valve; a back pressure chamber that is formed on the other side and into which pressurized oil flows for closing the valve; an on-off valve comprising a communicating passage having functionality to generate a pressure differential between the positive pressure chamber and the back pressure chamber; a pilot valve by which the back pressure chamber selectively communicates with a portion having lower pressure than the back pressure chamber; and a low pressure oil supply portion into which flows pressurized oil of relatively lower pressure than the oil pressure supplied to the positive pressure chamber; wherein said device comprises a means for opening the pilot valve and having the back pressure chamber communicate with the low pressure oil supply portion, and supplying pressurized oil to the back pressure chamber from the low pressure oil supply portion when the on-off valve opening operation is slower than a preset threshold value.