It is sought to provide a rear casing arrangement for a magnetic drive pump, which can sufficiently provide such functions pressure resistance and heat resistance, which give rise to problems in the case of manufacturing the rear casing from a material based on a synthetic resin, and can also be manufactured at low cost.A reinforcing belt-like ring member is woundly fitted on the outer periphery of a cylindrical barrel part of an inner casing member constituting a rear casing. The belt-like ring member has a width smaller than the length of the barrel part. A casing cover member is fitted on the belt-like ring member in the above fitted state. Alternatively, it is possible to fit the belt-like ring member on the outer periphery of a barrel part of the casing cover member. These parts can be disassembled.