The invention discloses a side recognizing device for a pencil printer. A transversely-penetrating mounting hole is formed in the middle of a shell of a pencil position change device, a pencil position change shaft is arranged in the mounting hole in a freely-rotating mode, a pencil clamping sleeve is arranged in the pencil position change shaft and is pressed tightly and fixed by a compression screw located at the inlet end of the pencil position change shaft; one end of a position change crank is fixed to the outlet end of the pencil position change shaft; a color sensor is arranged above the inlet end of the pencil position change shaft, a position sensor is arranged rightly facing the limiting position of the position change crank, and a piston rod of an air cylinder is connected with the other end of the position change crank through a linkage device and drives the position change crank to do deflection movements. The side recognizing device overcomes the defect that traditional pencil side recognition printing is low in speed, can automatically recognize pencil printing sides, greatly reduces labor intensity of workers, basically avoids face recognition errors and reduces rejection rates; meanwhile, the pencil printing speed is not influenced by position change of pencils, and the production efficiency is greatly improved.