A uniaxial eccentric screw pump enabling a stator to be easily separated into an outer cylinder and a lining member, and being capable of solving problems such as a positional shift and deformation of the lining member, and an occurrence of uneven wear and an unstable discharge amount associated with the positional shift and deformation. The stator includes a liner portion having a cylindrical shape and being integrally formed so as to have an inner peripheral surface of an internal thread type and an outer cylinder portion. The liner portion includes, at both end portions thereof, flange portions protruding radially outward, and an outer cylinder mounting portion is provided between the flange portions. The outer cylinder portion is mounted in a non-bonded state on the outer cylinder mounting portion, and both end portions of the outer cylinder portion abut on the flange portions, respectively.