The invention discloses a door release device. The door release device comprises an outer casing (1), a mechanical device outer casing (12), a slide rod (13) with a slide block, a mechanical door closer (14) and a transmission device, wherein the transmission device is positioned in the mechanical device outer casing (12), and is connected with one end of the slide rod (13) with the slide block in a clamping way; the other end of the slide rod (13) with the slide block is connected with the mechanical door closer (14); the mechanical device outer casing (12) and the slide rod (13) with the slide block are positioned in the inner side of the outer casing (1). The door release device has the advantages that for the door requiring frequent opening, when the door release device works, the power consumption is not needed, and the power is only instantaneously supplied when the door is closed, so that the energy-saving and environment-friendly effects are realized; (2) when the sliding double doors are installed, the left and right parts do not need to be distinguished, so that the manual cost is reduced in engineering application; the economic value and social value are larger.