Abstract: The present disclosure provides an auxiliary device for sleeping on a seat. The auxiliary device for sleeping on a seat includes a pillow. The pillow can be stably connected to a seat headrest through assembly parts. An eye mask is arranged on the side, away from the seat headrest, of the pillow. The eye mask has the function of isolating external light. Therefore, the rest quality of people is improved, and accidents can also be prevented. In addition, the eye mask is detachably connected with the pillow through the hook-and-loop fasteners, and the assembly parts can be quickly disassembled and assembled by using binding bands and connecting buckles, so that the using efficiency of the device is improved.