An eye mask for sleeping has a headband and two eyecups. The headband comprises an inner surface and an outer surface. The two eyecups are configured to cover two eyes respectively. Each eyecup has an adhering surface, a contact surface, and multiple first passages. The adhering surface is securely mounted on the inner surface of the headband. The contact surface is configured to cover one of the eyes of the user. The first passages are formed through each eyecup and extend from the adhering surface to the contact surface. With the eyecups mounted on the headband and configured to cover the eyes of the user, because the first passages are formed through the eyecups, heat and moisture can be dissipated and drained via the first passages.