To prevent air guided from the inside of a casing to the inside of an auxiliary tank from again entering the casing by providing a connecting port of the casing in an electric well pump with a partition plate for dividing the port into two parts, and also providing a partition plate in a connecting port of the auxiliary tank to divide the port into two parts.

This electric well pump 1 is formed by an auxiliary tank 2, a casing 3 and a cover, and the auxiliary tank 2 has a tank side connecting port 4 provided on the contact surface with the casing 3, a discharge port 6 connected to a faucet through a piping 5, a filling port 7 for filling the auxiliary tank 2 and the casing 3 with priming, and a cap 8 for covering the filling port 7. In this case, in a water passage 12 of the casing 3, a casing side connecting port 9 part is provided with a partition plate 13, thereby dividing the connecting port 9 into two parts. A connecting port 4 of the auxiliary tank 2 is provided with a partition plate 14 formed on an extension of the partition plate 13, thereby dividing the connecting port 14 into two parts. Thus, air and water can be separated efficiently.