The invention provides an intermediate storage device of an electrostatic coating system that can clean efficiently, a method for cleaning the same, and a method for coating. An intermediate storage device 10 comprises: a first hole 141 which is open to a cylinder chamber 14 and is connected to a paint supply source; a second hole 142 which is open to the cylinder chamber 14 and is connected to a coating gun; and a switch means which switches between a first cleaning which cleans the cylinder chamber 14 by supplying cleaning fluid W from the first hole 141 and discharging from the second hole 142 waste fluid that has undergone cleaning and a second cleaning which cleans the cylinder chamber 14 by supplying cleaning fluid W from the second hole 142 and discharging from the first hole 141 waste fluid that has undergone cleaning.