A key structure with mechanical switch includes a keycap, a support plate board disposed under the keycap, a scissor unit, a receiving housing, a guiding outer cylinder, a rotating inner cylinder and an elastic element. The scissor unit guides the keycap up or down along a pressing direction. The receiving housing has a plurality of sectional boards and a plurality of sectional cutouts. The guiding outer cylinder is movably received in the receiving housing along the pressing direction, and abuts against a bottom surface of the keycap. The guiding outer cylinder has a plurality of positioning bumps and a plurality of lodging recesses. The rotating inner cylinder is received in the guiding outer cylinder and has a plurality of sliding bumps. The elastic element is located in the rotating inner cylinder to provide elasticity toward the keycap. The present disclosure also provides a mechanical switch.