The invention discloses a sliding groove type automatic window closing device which comprises a device body, a positioning seat and a rocker arm, wherein the two end of the rocker arm are respectivelyin pivot connection with the device body and the positioning seat. The device body comprises a sliding groove, a locking mechanism and an unlocking mechanism, wherein the locking mechanism is arranged in the sliding groove and used for locking the rocker arm, and the unlocking mechanism is used for driving the rocker arm to slide relative to the device body and close a window in a sliding mode. The unlocking mechanism comprises a positioning frame, an unlocking frame, an elastic part and a temperature sensing glass ball, wherein the positioning frame is arranged on the sliding groove, and theunlocking frame is movably connected with the positioning frame and extends along the length direction of the sliding groove. When a fire occurs, the temperature sensing glass ball is exploded alongwith the rising of the indoor temperature, the elastic part restores deformation, pushes the unlocking frame to the locking mechanism, and unlocks the locking mechanism. The sliding groove type automatic window closing device is sensitive in response. When the fire occurs, the window can be quickly and accurately closed, and the fire can be effectively prevented from spreading. Meanwhile, the sliding groove type automatic window closing device is simple in structure, convenient to use, and low in cost.