PURPOSE: To improve and maintain the efficiency of pump by baking a rubber to the inside of a first intermediate casing to form a rubber part and sealing the inner peripheral end part of said rubber part and an impeller, while also sealing the top end part of said rubber part and a second intermediate casing.

CONSTITUTION: A part between a first intermediate casing 7 on the inner surface of which a rubber part 7a is formed, and an impeller 9 is sealed by the inner peripheral end part of the rubber part 7a, while the first intermediate casing 7 and a second intermediate casing 6 are sealed by the upper end part of the rubber part 7a. The rubber part 7a is formed by the baking of a rubber. Since the rubber part 7a is provided in an integrated form with the inner surface of the first intermediate casing 7, sufficient strength can be obtained even if the first intermediate casing is made of a plate metal, and both of the intermediate casing 6, 7 can be concentrically arranged, and wear resistance against a foreign matter such as sand, etc. can be improved due to the rubber part 7a, increasing the efficiency of a pump for a long period of time.