A light emitting key structure is provided. The key structure includes a base, a reflective sheet, a circuit board, an elastic member, a linkage mechanism, and a key cap sequentially disposed one on another in order. The reflective sheet is disposed on the base. The circuit board is made of a light guide material. At least one light source is bonded to a lateral side of the circuit board. The circuit board, together with the light source bonded to the lateral side thereof is disposed on the reflective sheet. The elastic member is directly coupled to the circuit board. The key cap is featured with a light transmission characteristic. Therefore, in operation, a light emitted from the light source can be directly guided into the circuit board, and then outputted from the light transmissive key cap, thus achieving the light emitting effect.