A thrust-action mechanical pencil having a lead-forwarding mechanism and an outer sleeve, the lead-forwarding mechanism being inserted from the rear end of the outer sleeve. An elastic member to prevent looseness is inserted between a chuck ring sleeve, and an inner ring provided on the inside of the outer sleeve to prevent forward movement. A tubular retaining sleeve having a full length slit is installed between a mouth piece and a stepped portion of the lead forewarding mechanism. A retaining portion on the forward end of the retaining sleeve is set between the mouth piece and the forward end of the outer sleeve to retain the lead-forwarding mechanism in the pencil.