1. A contactless switching apparatus comprising: a. a fixed yoke made of a magnetic material which is formed in a U shape so that it has a pair of parallel free-ended segments, b. a base made of a non-magnetic material to which said fixed yoke is secured so that both free-ended segments of the fixed yoke face upward, c. at least one magnetro-resistance effect device which is mounted on a side opposing to the other free-ended segment of one of the free-ended segments of said fixed yoke, d. at least one terminal pin made of a conductive material which is arranged near the frEe-ended segment at which said magnetroresistance effect device is fixed, is fixed to the base under which its lower end is projected and is connected with a lead of said magnetro-resistance effect device, e. a magnet which is arranged between said both free-ended segments so that both magnetic poles are positioned to respectively oppose to said both free-ended segments of the fixed yoke and a magnetic path is formed between said freeended segments and the magnet, f. a support member which supports said magnet and can be vertically slid, g. a switch case which is open at its lower side to cover said base, houses said fixed yoke, terminal pins and magnet, and is provided with a through hole at its upper surface through which said support member slides in a vertical direction and guideways being located inside said switch case to guide said support member in a vertical direction, h. a key top which is mounted on the upper part of said switch case, coupled to the upper end of the support member and is constructed so that it can be lowered by manual depression and, i. a spring member which provides resilient force to return said key top to the home position.