A working fluid supply system (100, 200) configured to supply working fluid to a fluid apparatus, the working fluid supply system (100, 200) comprising: a first pump and a second pump driven by output from a common driving source, the first pump and the second pump being capable of supplying working fluid to the fluid apparatus through a supply passage; a valve device (24, 124, 125, 126) configured to cause a discharge passage of the second pump to communicate with at least one of the supply passage and another passage different from the supply passage; and a control unit configured to change a communication state of the valve device (24, 124, 125, 126) in accordance with a required flow amount (Qr) of the working fluid required by the fluid apparatus, wherein the valve device (24, 124, 125, 126) has: a first communication state at which the discharge passage is communicated only with the supply passage; and a second communication state at which the discharge passage is communicated only with the another passage, characterized in that the valve device (24, 124, 125, 126) further has a third communication state at which the discharge passage is communicated with the supply passage and the another passage while the first communication state is shifted to the second communication state or while the second communication state is shifted to the first communication state, and the control unit is: configured to set switching time for switching the communication state of the valve device (24, 124, 125, 126) in accordance with a degree of a pressure variation predicted to be caused in the supply passage when the communication state of the valve device (24, 124, 125, 126) is switched instantaneously from the first communication state to the second communication state or from the second communication state to the first communication state; and configured to switch the communication state of the valve device (24, 124, 125, 126) from the first communication state to the second communication state or from the second communication state to the first communication state via the third communication state by spending the set switching time. a first pump and a second pump driven by output from a common driving source, the first pump and the second pump being capable of supplying working fluid to the fluid apparatus through a supply passage; a valve device (24, 124, 125, 126) configured to cause a discharge passage of the second pump to communicate with at least one of the supply passage and another passage different from the supply passage; and a control unit configured to change a communication state of the valve device (24, 124, 125, 126) in accordance with a required flow amount (Qr) of the working fluid required by the fluid apparatus, wherein the valve device (24, 124, 125, 126) has: a first communication state at which the discharge passage is communicated only with the supply passage; and a second communication state at which the discharge passage is communicated only with the another passage, characterized in that the valve device (24, 124, 125, 126) further has a third communication state at which the discharge passage is communicated with the supply passage and the another passage while the first communication state is shifted to the second communication state or while the second communication state is shifted to the first communication state, and the control unit is: configured to set switching time for switching the communication state of the valve device (24, 124, 125, 126) in accordance with a degree of a pressure variation predicted to be caused in the supply passage when the communication state of the valve device (24, 124, 125, 126) is switched instantaneously from the first communication state to the second communication state or from the second communication state to the first communication state; and configured to switch the communication state of the valve device (24, 124, 125, 126) from the first communication state to the second communication state or from the second communication state to the first communication state via the third communication state by spending the set switching time. configured to set switching time for switching the communication state of the valve device (24, 124, 125, 126) in accordance with a degree of a pressure variation predicted to be caused in the supply passage when the communication state of the valve device (24, 124, 125, 126) is switched instantaneously from the first communication state to the second communication state or from the second communication state to the first communication state; and configured to switch the communication state of the valve device (24, 124, 125, 126) from the first communication state to the second communication state or from the second communication state to the first communication state via the third communication state by spending the set switching time.