In a dipping type pump where a rotary shaft extending from a motor into a pump casing disposed in liquid is mounted with impellers, and liquid is sucked from a sucking port at a lower portion of the casing and discharged from a discharge port by rotational driving of the motor, where a check valve for air purge which allows outflow of gas from the interior of the casing but prevents outflow of liquid therefrom is provided at an upper portion of the casing.