A rotary connector device, comprising: a stator and a rotator which rotates with respect to the stator concentrically with a steering; an accommodating space having a ring shape in a plan view, which is formed inside the stator and the rotator, and which accommodates a flat cable for electrically connecting the rotator and the stator in a wound state; and a retainer which is located on a bottom surface of the accommodating space so as to be able to guide the cable to rotate concentrically with the steering, wherein: the rotator includes an inner peripheral tube portion which forms an inner peripheral surface of the accommodating space; an inner wound portion (Ci) of the flat cable is wound around the inner peripheral tube portion of the rotator; a rotator side abutting portion is formed on a lower portion of the inner peripheral tube portion; a retainer side abutting portion is formed on an upper surface inner peripheral portion of the retainer; the rotator side abutting portion abuts the retainer side abutting portion in a slidable manner; a protruding abutting portion (27T, 47T) is formed on at least one of the rotator side abutting portion and the retainer side abutting portion so as to protrude toward the other; a trench portion is formed in the retainer radially external to the retainer side abutting portion; and the trench portion is formed into a trench shape which has a deepest portion next to the retainer side abutting portion and an inclined surface which becomes gradually shallower from the deepest portion toward the radially external direction of the retainer; characterized in that the upper surface inner peripheral portion of the retainer comprises a flat portion that supports the inner wound portion (Ci) of the flat cable; and the inclined surface of the trench portion extends from the deepest portion toward the radially external direction until the inclined surface reaches the flat portion that supports the inner wound portion (Ci) of the flat cable. a stator and a rotator which rotates with respect to the stator concentrically with a steering; an accommodating space having a ring shape in a plan view, which is formed inside the stator and the rotator, and which accommodates a flat cable for electrically connecting the rotator and the stator in a wound state; and a retainer which is located on a bottom surface of the accommodating space so as to be able to guide the cable to rotate concentrically with the steering, wherein: the rotator includes an inner peripheral tube portion which forms an inner peripheral surface of the accommodating space; an inner wound portion (Ci) of the flat cable is wound around the inner peripheral tube portion of the rotator; a rotator side abutting portion is formed on a lower portion of the inner peripheral tube portion; a retainer side abutting portion is formed on an upper surface inner peripheral portion of the retainer; the rotator side abutting portion abuts the retainer side abutting portion in a slidable manner; a protruding abutting portion (27T, 47T) is formed on at least one of the rotator side abutting portion and the retainer side abutting portion so as to protrude toward the other; a trench portion is formed in the retainer radially external to the retainer side abutting portion; and the trench portion is formed into a trench shape which has a deepest portion next to the retainer side abutting portion and an inclined surface which becomes gradually shallower from the deepest portion toward the radially external direction of the retainer; characterized in that the upper surface inner peripheral portion of the retainer comprises a flat portion that supports the inner wound portion (Ci) of the flat cable; and the inclined surface of the trench portion extends from the deepest portion toward the radially external direction until the inclined surface reaches the flat portion that supports the inner wound portion (Ci) of the flat cable. the rotator includes an inner peripheral tube portion which forms an inner peripheral surface of the accommodating space; an inner wound portion (Ci) of the flat cable is wound around the inner peripheral tube portion of the rotator; a rotator side abutting portion is formed on a lower portion of the inner peripheral tube portion; a retainer side abutting portion is formed on an upper surface inner peripheral portion of the retainer; the rotator side abutting portion abuts the retainer side abutting portion in a slidable manner; a protruding abutting portion (27T, 47T) is formed on at least one of the rotator side abutting portion and the retainer side abutting portion so as to protrude toward the other; a trench portion is formed in the retainer radially external to the retainer side abutting portion; and the trench portion is formed into a trench shape which has a deepest portion next to the retainer side abutting portion and an inclined surface which becomes gradually shallower from the deepest portion toward the radially external direction of the retainer; characterized in that the upper surface inner peripheral portion of the retainer comprises a flat portion that supports the inner wound portion (Ci) of the flat cable; and the inclined surface of the trench portion extends from the deepest portion toward the radially external direction until the inclined surface reaches the flat portion that supports the inner wound portion (Ci) of the flat cable.