A rotating electrical machine includes: a rotor core in which a slot passing therethrough is provided; a rotor winding which coil end portion is extended on the axially outer side than the core end face of the rotor core; a U-shaped channel which is arranged on the slot of the rotor core, is touched to come into contact with a bottom portion of the rotor winding, and is axially extended to be projected on the axially outer side than the core end face of the rotor core; a slot cell which insulates the rotor winding and the U-shaped channel from the rotor core; and an interposed piece arranged between the rotor windings at a portion more projected than the core end face of the rotor core. The projected end face of the U-shaped channel is arranged on the axially inner side than the projected end face of the interposed piece.