PURPOSE: To obtain the compact structure of a pump by effectively utilizing the space formed in the pump and facilitate transport and installation and prevent breakage by forming a vacant space inside the suspended leg part of the installation base on which the pump is mounted and by accomodating and accumulator in this vacant space.

CONSTITUTION: On the upper surface of a installation base 11 made of steel plate, a pump 1 and its driving motor are mounted. The installaton base is equipped with the suspended leg part 112 formed by press working, the vacant part 113 formed inside the suspended leg part, and the pressure storing chamber 12 which is formed by pressing a part 111 of the installation base 11 downward and protruding it into the vacant space 113. As the pressure storing chamber 12 is accomodated in the vacant space 113 inside the suspended leg part 112 of the installation base 11 on which the pump 1 is mounted effective utilization of the space can be permitted, and a compact structure can be obtained, and transport and installation can be facilitated, and breakage can be prevented, since the installation base 11 serves for preventing the impact from outside.