The invention provides a key module and a portable electronic device using the key module. The key module comprises a key cover and a key seat. An accommodating room is formed on the key seat. The key cover can be accommodated in the accommodating room in the sliding manner. The key module further comprises a shooting triggering mechanism and a focusing triggering mechanism. A first contact and two latching clasps which are symmetrically arranged relative to the first contact are convexly arranged on the surface of the key seat, facing the key cover. The key seat also comprises a bottom wall of the accommodating room for forming the accommodating room. The bottom wall of the accommodating room is opened with a through hole and two grooves crossing the bottom wall of the accommodating room. The first contact is arranged at one end of the through hole. Each latching clasp is matched with one groove in the sliding manner to prevent the key cover from leaving the key seat. When the key cover moves along a pressing path thereof, the first contact crosses the through hole and triggers a shooting triggering mechanism and one of the latching clasps triggers a focusing triggering mechanism.