The invention provides a device for measuring permeability coefficient of a rock sample. The device at least comprises a measuring box, and a head water-permeable board and a tail water-permeable board which are located in an inner chamber of the measuring box. The inner chamber of the measuring box is divided by the head water-permeable board and the tail water-permeable board into a water feeding chamber, a rock sample chamber, and a water-permeable chamber in sequence. A water inlet communicates with the water-permeable chamber, and a water outlet communicates with the water-permeable chamber. A wall of the water feeding chamber is equipped with a drain valve communicating with the water feeding chamber. A wall of the rock sample chamber is equipped with a transparent inspection window, the rock sample chamber is internally provided with a waterproof sealing film matching a side surface of a rock sample. The head water-permeable board, the waterproof sealing film, and the tail water-permeable board form a seepage channel. The head and tail water-permeable boards are made of water-permeable stone and elastic sealing strips. A water-permeable system of the water-permeable stone comprises a big hole located in the middle and small holes uniformly dispersed around the big hole in an annular manner, or comprises more than two water-permeable holes which are uniformly dispersed and communicate to each other. The device is simple in structure and accurate in measurement results, and is suitable for a board-shaped rock sample with cracks inside.