The present invention relates to a locking device for a door of a pen and, more specifically, to a locking device for fixing a door of a pen installed to be rotated to a column installed to be adjacent to the door. The locking device includes a pair of supporting members which is vertically formed on the end of the door of the pen at a predetermined interval and joined to the end of the door； a pair of rotary shafts which is vertically installed between the supporting members to be rotated and to be horizontally separated at a predetermined interval； first and second fixing members which are composed of a body including an insertion groove to be fitted and joined to the rotary shaft and a fixing bar which is extended from the body and closely adheres to the outer circumference of the column and which are fitted and joined to the rotary shafts and rotated with the rotary shafts； a first fixture which is joined to the upper part of the body of the first fixing member and which includes a fitting groove which a screw thread is formed on the inner circumference； a second fixture which is joined to the upper part of the body of the second fixing member and which includes a fitting groove which a screw thread is formed on the inner circumference； and a fixing screw which is inserted into each fitting groove of the first and second fixing members to be penetrated through and which fixes the first and second fixing members. The present invention prevents the fixing bars from being crashed to the column by rotating the first and second fixing members to the outer side when rotating the door of the pen. The present invention fixes the door of the pen to the column by inserting the fixing screw into the fitting grooves of the first and second fixing members after rotating the fixing bars of the first and second fixing members to the inner side to closely adhere to the column when fixing the door of the pen to the column.본 발명은 축사용 문 잠금장치에 관한 것으로, 더욱 상세하게는 회전 가능하게 설치되는 축사용 문을 상기
