A hydraulic system comprising: an actuator for working machine; a hydraulic pump; a pilot-type control valve which supplies an operating oil pressure (Pp) from the hydraulic pump to the actuator; a pilot pressure source; an electromagnetic proportional valve which supplies a pilot pressure to the control valve when receiving an electromagnetic proportional valve supply pressure from the pilot pressure source; an operation lever which receives an operation for operating the actuator; a controller which controls the electromagnetic proportional valve based on an operation signal from the operation lever; and a pilot pressure switching unit in which the electromagnetic proportional valve supply pressure is capable of being switched, the hydraulic system being characterized in that the control valve has a bleed-off passage whose opening area increases and decreases according to a stroke of a spool based on the pilot pressure, and is capable of controlling the operating oil pressure (Pp) to be supplied to the actuator according to the opening area, during an emergency operation in which the controller is not capable of controlling the electromagnetic proportional valve, the electromagnetic proportional valve is brought into a fully opened state, the pilot pressure switching unit switches the electromagnetic proportional supply pressure from a first pressure to a second pressure in order to prevent generation of an operating oil pressure (Pp) capable of activating the actuator, when an operating oil with a minimum discharge amount passes through the bleed-off passage, the first pressure being a pressure during normal operation, the second pressure being a pressure smaller than the first pressure, and as the operating oil discharge amount from the hydraulic pump increases and decreases, the operating oil pressure (Pp) increases and decreases, and an operation speed of the actuator is controlled. an actuator for working machine; a hydraulic pump; a pilot-type control valve which supplies an operating oil pressure (Pp) from the hydraulic pump to the actuator; a pilot pressure source; an electromagnetic proportional valve which supplies a pilot pressure to the control valve when receiving an electromagnetic proportional valve supply pressure from the pilot pressure source; an operation lever which receives an operation for operating the actuator; a controller which controls the electromagnetic proportional valve based on an operation signal from the operation lever; and a pilot pressure switching unit in which the electromagnetic proportional valve supply pressure is capable of being switched, the hydraulic system being characterized in that the control valve has a bleed-off passage whose opening area increases and decreases according to a stroke of a spool based on the pilot pressure, and is capable of controlling the operating oil pressure (Pp) to be supplied to the actuator according to the opening area, during an emergency operation in which the controller is not capable of controlling the electromagnetic proportional valve, the electromagnetic proportional valve is brought into a fully opened state, the pilot pressure switching unit switches the electromagnetic proportional supply pressure from a first pressure to a second pressure in order to prevent generation of an operating oil pressure (Pp) capable of activating the actuator, when an operating oil with a minimum discharge amount passes through the bleed-off passage, the first pressure being a pressure during normal operation, the second pressure being a pressure smaller than the first pressure, and as the operating oil discharge amount from the hydraulic pump increases and decreases, the operating oil pressure (Pp) increases and decreases, and an operation speed of the actuator is controlled.