The invention discloses a magnet door lock. A first portion comprises: a frame provided with a cylinder channel; a cylinder slidably disposed in the cylinder channel and internally provided with a channel hole, wherein the side of the cylinder is provided with a groove; a first magnet connected to an outer end of the cylinder; a first spring disposed in the channel hole and connected at one end to the cylinder and the other end to the bottom of a lock channel. A second portion comprises: a door body provided with the lock channel; an attracting mechanism disposed in the lock channel and attractive with the first magnet; a fastening mechanism fastened in the groove of the cylinder; a switch mechanism acting on the fastening mechanism and the attracting mechanism and used for rotating the attracting mechanism and opening the fastening mechanism. Whether to automatically lock or not can be automatically selected according to a user's need, the cylinder can be kept in the cylinder channel constantly except for the time of locking, and living safety is improved; the magnet door lock is simple in structure, convenient to use, low in manufacture cost and widely applicable to the market.