A key switch preferably used for a keyboard as an input device in electronic equipment. The key switch includes a base section; a key top disposed above the base section; a pair of link members interlocked to each other to support and direct the key top in a vertical direction relative to the base section; a switch member including a contact section capable of opening and closing in response to a vertical movement of the key top; and a biasing member capable of applying an elastic biasing force in a vertically upward direction to the key top. The key switch further includes a protection member disposed and inserted between the base section and the key top at a position where the protection member surrounds the pair of link members, the contact section and the biasing member. The protection member is elastically deformed to follow the vertical movement of the key top, and protects the pair of link members, the contact section and the biasing member from penetration of foreign matter.