The invention discloses a horizontal plate mop, and relates to the field of cleaning tools. The horizontal plate mop comprises a mop head and a mop rod, wherein the mop head and the mop rod are connected, the mop rod comprises a handle, a first connecting rod, a second connecting rod and a locking sleeve, the handle, the first connecting rod, the locking sleeve and the second connecting rod are sequentially connected through sleeving into a whole, one end of the second connecting rod is connected with the mop head, a self-locking device is arranged in the locking sleeve, one end of the self-locking device sleeves in the first connecting rod, and the other end of the self-locking device sleeves in the second connecting rod. The horizontal plate mop is simple and compact in structure, and good in connecting effect, length adjustment can be carried out according to use occasions, during use, the mop rod can not have section separation, in addition, the mop can adapt to the cleaning requirements of different positions, the dead corners of sanitation are avoided, moreover, the self-locking device is slightly screwed through the locking sleeve, then the tight locking of the self-lockingdevice is completed, the mop rod then can be rapidly assembled, and the assembly process is simple.