A piston for dual-directional hand inflator comprises a main body (1) having an internal hole (11) and an external hole (12). A plurality of spacers (17) are disposed between the top surface and the bottom surface of the main body (1) and divide a space into a gas-intake guide chamber (3) and a gas-exhaust guide chamber (5). The gas-intake guide chamber (3) communicates with the internal hole (11), and the gas-exhaust guide chamber (5) communicates with the external hole (12). A first cover plate (6) is disposed at an end of the gas-intake guide chamber to seal the gas-intake guide chamber. A second cover plate (7) is disposed at an end of the gas-exhaust guide chamber to seal the gas-exhaust guide chamber. There is only two cover plate to be adhered and fixed. The assembly is more convenient and the leakage probability is reduced.