A lock for separably fixing a door to a cabinet having an introduction port therein, the lock comprising: a holder for provision at one selected from between the cabinet and the door; a housing for provision at the other selected from between the cabinet and the door; a first stopper provided at the housing; an actuation unit configured to reciprocate in the housing, the actuation unit being configured to be moved by the holder when the holder is brought into contact with the actuation unit; a fastening unit supported by the first stopper, the fastening unit being configured to be separated from the first stopper and coupled to the holder when the actuation unit is moved by the holder; a first elastic member for providing force necessary to separate the fastening unit from the first stopper; and a second elastic member (981, 983) for providing force necessary to move the actuation unit back so that the fastening unit is supported by the first stopper, characterised in that the fastening unit comprises: a fastening body separably provided at the first stopper, the fastening body being coupled to the holder when separated from the first stopper; and a first body and a second body extending from opposite ends of the fastening body so as to be distant from the introduction port when in place, and the actuation unit comprises: a first slide and a second slide configured to reciprocate in the direction parallel to the movement path of the holder, the first slide and the second slide being spaced apart from each other so as to define a space for receiving the first body and the second body; a transfer part for connecting the first slide and the second slide, the transfer part being configured to be moved by the holder; and a body push part (913, 943) provided on at least one selected from between the first slide and the second slide for contacting the first body and the second body depending on a position of the transfer part to separate the fastening body from the first stopper. a holder for provision at one selected from between the cabinet and the door; a housing for provision at the other selected from between the cabinet and the door; a first stopper provided at the housing; an actuation unit configured to reciprocate in the housing, the actuation unit being configured to be moved by the holder when the holder is brought into contact with the actuation unit; a fastening unit supported by the first stopper, the fastening unit being configured to be separated from the first stopper and coupled to the holder when the actuation unit is moved by the holder; a first elastic member for providing force necessary to separate the fastening unit from the first stopper; and a second elastic member (981, 983) for providing force necessary to move the actuation unit back so that the fastening unit is supported by the first stopper, characterised in that the fastening unit comprises: a fastening body separably provided at the first stopper, the fastening body being coupled to the holder when separated from the first stopper; and a first body and a second body extending from opposite ends of the fastening body so as to be distant from the introduction port when in place, and the actuation unit comprises: a first slide and a second slide configured to reciprocate in the direction parallel to the movement path of the holder, the first slide and the second slide being spaced apart from each other so as to define a space for receiving the first body and the second body; a transfer part for connecting the first slide and the second slide, the transfer part being configured to be moved by the holder; and a body push part (913, 943) provided on at least one selected from between the first slide and the second slide for contacting the first body and the second body depending on a position of the transfer part to separate the fastening body from the first stopper.