The invention relates to the technical field of music instruments and specifically relates to a piano key automatic playing device, in particular to a device for driving piano keys to play automatically through electromagnets, which is characterized in that the vertical frame electromagnets with serrated distribution and arrangement are connected on the front surface and the back surface of a vertical mounting plate respectively, an ejector rod of each frame electromagnet penetrates an independent ejector rod hole of a piano middle plate, a buffer cap is inserted in the part at the top end ofthe upper surface of the middle plate, a row of intermittent kidney-shaped slot penetrating screws are arranged at the upper part of the mounting plate for connecting a plurality of adapter angles onthe front surface and the back surface of the mounting plate respectively, a plurality of rows of equidistant intermittent kidney-shaped slots are arranged between the upper part and the lower part of the mounting plate, and the penetrating screws connect the frame electromagnets on the front surface and the back surface of the mounting plate respectively. Compared with the prior art, the device has the advantages of novel design, firm structure, reliable use, convenient manufacture, small affects on the piano structure, no damage to the piano middle plate, low cost, simple production and mounting, strong versatility, large power margin of the electromagnets and easy heat dissipation.