A pushbutton mechanism for keyboards includes a bridge in a pushbutton that has an inner frame and an outer frame to make the pushbutton movable up and down. The inner frame and outer frame are intersected and coupled together, and have respectively inner side brackets and outer side brackets that have a stub shaft and a pivot portion to form a relative turning relationship. The inner and outer side brackets have respectively harness bosses and harness recesses corresponding to each other to allow the pushbutton to form a lifting position and a lower position in normal conditions. The bridge thus formed can generate a steadier relative turning and confine the stroke distance for the pushbutton.