A barrel-type multistage pump with uniformed velocity distribution in an axial direction, on a cross-section of a rotating flow channel, to suppress fluid loss in a last stage, and including: plural stages of centrifugal impellers, covered by an inner casing; diffusers and return channels provided on downstream sides of said centrifugal impellers, to guide the flow of a fluid to a centrifugal impeller in the next stage, and return vanes arranged at respective return channels; a cylindrical outer casing having a suction pipe and a discharge pipe, wherein a cylindrical rotating flow channel connected to a discharge opening is provided between an outer casing and an inner casing, a connecting channel to connect between a rotating flow channel and diffusers.