RESERVOIR TANK

An object of the invention is to provide a reservoir tank which can suppress the air bubbles flowing into the tubular projecting portion, regardless of the position of such projecting portion. The reservoir tank includes a reservoir body which reserves a fluid in an inner portion thereof formed to be in a hollow box shape. The reservoir body includes a port extending outward, a reservoir chamber which reserves the fluid and a port chamber which volume is smaller than that of the reservoir chamber and is in fluid communication with the port and a first communication passage positioned at a portion lower than a changeable liquid surface of the fluid reserved in the reservoir chamber in a vertical direction and provided at the first partition portion to allow the fluid communication between the reservoir chamber and the port chamber and wherein the port chamber and the port are kept being a state in which they are filled with the fluid supplied from the reservoir chamber via the first communication passage. 本发明的