The present invention relates to a button-sliding-type opening/closing device for a cosmetic container consisting of a vessel for storing cosmetics in a liquid or gel state, and a discharge pump coupled to a top inner portion of the vessel for discharging cosmetics by applying external pressure thereto, wherein the button-sliding-type opening/closing device comprises: a shoulder (20) coupled to the top portion of the vessel (10); a button body (30) inserted into the shoulder (20) and upwardly and downwardly movable; and a button (40) slidably coupled to a top surface of the button body (30), for opening and closing a cosmetic pumping hole (31) in the button body (30), as well as for preventing the button body (30) from being pressed and actuated.