A switching unit (30,46) for switching pressure in a pressure-switching target chamber of a hydraulic machine which includes the pressure-switching target chamber, a high pressure oil line, and a low pressure oil line, the switching unit (30, 46) comprising a spool valve (40,48) which comprises: a first chamber (34,140); a second chamber (36,142); and a spool (38,144) including a first pressure-receiving surface (42,146) formed so as to receive hydraulic pressure of the first chamber (34,140) and a second pressure-receiving surface (44,148) formed so as to receive hydraulic pressure of the second chamber (36,142), the second pressure-receiving surface (44,148) having an area smaller than that of the first pressure-receiving surface (42,146), the spool valve (40,48) being configured to switch the hydraulic pressure of the first chamber (34,140) between pressure P 2 which is higher than pressure in the low pressure oil line and pressure P 1 which is lower than the pressure P 2, while maintaining the hydraulic pressure of the second chamber (36,142) at the pressure P 2, so that the spool (38,144) is moved and the pressure in the pressure-switching target chamber is switched, wherein the spool valve (40,48) comprises: a low-pressure port (70,128) configured to be in communication with a first hydraulic pressure line having the pressure P 1; a high-pressure port (68,120) configured to be in communication with a second hydraulic line having the pressure P 2; and an output port (66,124) configured to be in communication with the pressure-switching target chamber, and wherein a port which is in communication with the output port (66,124) is configured to be switched between the high-pressure port (68,120) and the low-pressure port (70,128), so that the pressure of the pressure-switching target chamber is switched between the pressure P 1 and the pressure P 2, wherein the switching unit further comprising a two-port solenoid valve configured to switch the hydraulic pressure of the first chamber between the pressure P 1 and the pressure P 2, wherein the spool valve comprises a first flow-path part configured to bring the high-pressure port into communication with the first chamber and a second flow-path part configured to bring the high-pressure port into communication with the second chamber, characterized in that the first flow-path part and the second flow-path part are disposed inside the spool (38, 144) and branched from a flow path that is configured to communicate with the high-pressure port to connect to the first chamber and the second chamber, respectively, and wherein the first flow-path part including a restricting portion. a first chamber (34,140); a second chamber (36,142); and a spool (38,144) including a first pressure-receiving surface (42,146) formed so as to receive hydraulic pressure of the first chamber (34,140) and a second pressure-receiving surface (44,148) formed so as to receive hydraulic pressure of the second chamber (36,142), the second pressure-receiving surface (44,148) having an area smaller than that of the first pressure-receiving surface (42,146), a low-pressure port (70,128) configured to be in communication with a first hydraulic pressure line having the pressure P 1; a high-pressure port (68,120) configured to be in communication with a second hydraulic line having the pressure P 2; and an output port (66,124) configured to be in communication with the pressure-switching target chamber, and