A hydraulic-pressure control device comprising: a regulator comprising: a housing; a control piston fluid-tightly and slidably fitted in the housing; an input chamber provided at a rear of the control piston; and an output chamber provided in front of the control piston; and an input-hydraulic-pressure control device (56, 184) configured to control hydraulic pressure in the input chamber to move the control piston forward to raise hydraulic pressure in the output chamber and configured to control the hydraulic pressure in the input chamber to move the control piston backward to reduce the hydraulic pressure in the output chamber, wherein the input-hydraulic-pressure control device (56, 184) comprises a moving-direction control unit configured to: when a difference that is a value obtained by subtracting an actual hydraulic pressure in the output chamber from a target hydraulic pressure in the output chamber is less than a pressurization-side set value, control the hydraulic pressure in the input chamber to move the control piston backward; and when the difference is greater than a reduction-side set value, control the hydraulic pressure in the input chamber to move the control piston forward, characterized in that: the input-hydraulic-pressure control device (56, 184) comprises a normal control unit configured to: raise the hydraulic pressure in the input chamber when the difference is greater than a pressurization threshold value; reduce the hydraulic pressure in the input chamber when the difference is less than a pressure-reduction threshold value; and hold the hydraulic pressure in the input chamber when the difference is between the pressurization threshold value and the pressure-reduction threshold value; and the pressurization-side set value is a value greater than the pressurization threshold value, and the reduction-side set value is a value less than the pressure-reduction threshold value. a regulator comprising: a housing; a control piston fluid-tightly and slidably fitted in the housing; an input chamber provided at a rear of the control piston; and an output chamber provided in front of the control piston; and an input-hydraulic-pressure control device (56, 184) configured to control hydraulic pressure in the input chamber to move the control piston forward to raise hydraulic pressure in the output chamber and configured to control the hydraulic pressure in the input chamber to move the control piston backward to reduce the hydraulic pressure in the output chamber, wherein the input-hydraulic-pressure control device (56, 184) comprises a moving-direction control unit configured to: when a difference that is a value obtained by subtracting an actual hydraulic pressure in the output chamber from a target hydraulic pressure in the output chamber is less than a pressurization-side set value, control the hydraulic pressure in the input chamber to move the control piston backward; and when the difference is greater than a reduction-side set value, control the hydraulic pressure in the input chamber to move the control piston forward, characterized in that: when a difference that is a value obtained by subtracting an actual hydraulic pressure in the output chamber from a target hydraulic pressure in the output chamber is less than a pressurization-side set value, control the hydraulic pressure in the input chamber to move the control piston backward; and when the difference is greater than a reduction-side set value, control the hydraulic pressure in the input chamber to move the control piston forward, characterized in that: the input-hydraulic-pressure control device (56, 184) comprises a normal control unit configured to: raise the hydraulic pressure in the input chamber when the difference is greater than a pressurization threshold value; reduce the hydraulic pressure in the input chamber when the difference is less than a pressure-reduction threshold value; and hold the hydraulic pressure in the input chamber when the difference is between the pressurization threshold value and the pressure-reduction threshold value; and raise the hydraulic pressure in the input chamber when the difference is greater than a pressurization threshold value; reduce the hydraulic pressure in the input chamber when the difference is less than a pressure-reduction threshold value; and hold the hydraulic pressure in the input chamber when the difference is between the pressurization threshold value and the pressure-reduction threshold value; and the pressurization-side set value is a value greater than the pressurization threshold value, and the reduction-side set value is a value less than the pressure-reduction threshold value.