Pump and using method thereof

The invention provides a pump and using method thereof, in which the part between a joint surface (33) of a first housing (29) and a joint surface (31) of a second housing (28) is sealed by a rope-shaped sealing part (34) made of an electrometric material. The sealing part (34) is embedded into a sealing groove (35) formed on the joint surface (33) of the first housing (29), and is compressed by the joint surface (31) of the second housing (28) at the predetermined compression rate in the depth direction of the sealing groove (35). and a high compression part (36) with the compression rate for the sealing part (34) higher than the predetermined compression rate is formed at the predetermined part in the length direction of the sealing groove (35).