A fold knife comprising a handle and a blade hinged to the handle. The fold knife further comprises a switch mechanism for manual and semi-automatic operation which is positioned in the inner chamber of the handle. The switch mechanism for manual and semi-automatic operation has a first position in which it is allowed to manually open the blade from the handle and a second position in which it is allowed to automatically open the blade from the handle. The fold knife is capable of easily switching between the manual operation condition and the semi-automatic operation condition by means of the switch mechanism for manual and semi-automatic operation.