The present invention provides a pump unit that includes at least one hydraulic pump with inlet and outlet ports formed therein, a pump case for accommodating the at least one hydraulic pump, the pump case having an opening through which the at least one hydraulic pump is insertable into the pump case, and a center section connected to the pump case in such a manner as to close the opening of the pump case. The center section forms a pair of inlet/outlet passages having first ends respectively communicating with the inlet and outlet ports of the at least one hydraulic pump and second ends opening to the outside of the center section through a pump case abutting surface of the center section, and a first charging passage having a first end through which working hydraulic fluid is fed into the center section and a second end opening to the outside of the center section through the pump case abutting surface of the center section. At least one of the pump case and the center section forms a communication passage for communication between the second ends of the pair of inlet/outlet passages and the second end of the first charging passage. A first hydraulic fluid feeding valve is also provided in the pump unit for allowing hydraulic fluid to flow from the first charging passage to the pair of inlet/outlet passages while preventing the reverse flow. The first hydraulic fluid feeding valve is installable through the pump case abutting surface of the center section or a center section abutting surface of the pump case.