A submergible motor pump including a vortex impeller (2) attached to an end of a motor shaft (3), a pump casing (21,23) attached to a motor casing (25) and accommodating the impeller (2) therein, a strainer (9) attached to the pump casing for introducing water to be sucked into the pump casing, and a bottom plate (11) supporting the strainer (9) from therebelow is disclosed. The pump casing comprises an intermediate casing member (21) and a lower casing member (23), which are detachable from each other. The pump casing has a configuration in which the upper side is open so that the flow passage formed in the lower casing member does not have a bag-shaped configuration. A plurality of legs (29) are provided on the lower side of the lower casing member (23) as being integral portions thereof. The legs (29) are spaced apart from each other and extend as far as the outer peripheral end of the lower casing member (23). The strainer (9) is provided around the outer peripheral end of the lower casing member in such a manner as to surround the outer periphery of the lower casing member (23). The lower casing member (23) is clamped between the bottom plate (11) and the intermediate casing member (21) by means of clamping bolts (13), thereby assembling together the bottom plate (11), the lower casing member (23) and the strainer (9) in one unit.