To provide an internal pump which has a filter installed regardless of the composition of cooling water piping for filtering a cooling water for a submergible motor.

In an internal pump using a water-cooled submergible motor which is water-cooled by introducing a cooling water from the cooling water leading-in part of a container into the inside of the container to a sealed container (23, 24') where motor composing parts including at least a motor shaft are accommodated, a cooling water lead-in part is provided with a detachable filter 8.