Knock-action mechanical pencil comprising a lead-forwarding mechanism (2) and an outer sleeve (1), said lead-forwarding mechanism being inserted from the rear end of said outer sleeve. An elastic member (5) for prevention of looseness is inserted between a chuck ring sleeve (3) which constitutes said lead-forwarding machanism and an inner ring (4) for prevention of forward movement which is provided on the inside of the outer sleeve. A retaining sleeve (10) having a slit (9) extending over the full length is inserted between a mouth part (7) and a radially outward projecting step-shaped part (8) behind the mouth part, of a forward member (6) which is connected to the chuck ring sleeve. A retaining part (11) which is provided at the forward end portion of the retaining sleeve is set between the mouth part of the forward member and the forward end of the outer sleeve.