A keyswitch includes a cap, internal and external sleeves, a resilient arm, a base having a pillar, and an elastic member abutting against the internal sleeve and the base. The internal sleeve jackets the pillar, abuts against the cap and has a first outer annular surface with a transverse slot. The external sleeve jackets the internal sleeve and has a protruding block movably inserted into the transverse slot for guiding the external sleeve to rotate and a second outer annular surface having concave and convex portions and an arc-shaped bar. When the resilient arm abuts against a second position on the convex portion and the cap presses the external sleeve, the resilient arm crosses the arc-shaped bar. When the resilient arm abuts against a first position on the convex portion and the cap presses the external sleeve, the resilient arm does not need to cross the arc-shaped bar.