To replenish battery fluid by a simple work procedure and quickly.

In an electric motor-driven pump 32, in accordance with a suction start command from a switch part 38, a fluid is sucked from a suction port to be fed out from a feed port, and in accordance with a feed stop command, feeding out of the fluid from the feed port is immediately stopped. A suction pipe part 34 can be inserted to a fluid take out port of a battery fluid storage tank 18, a through cap 36 screwable to the fluid take out port 17a is provided in this suction pipe part 34. A deformable feed pipe part 20 communicates with a feed port 32b of the electric motor-driven pump 32, a nozzle part 22 insertable to a fluid filler port 16 of a battery device 14 communicates with a tip end of this feed pipe part 20. A nozzle lock 24 locking the nozzle part 22 to the fluid filler port 16 is provided in a communication part between the feed pipe part 20 and the nozzle part 22.