PURPOSE: To discriminate the kind of a tape, by measuring the surface electric resistance of the tape which is in use, in a magnetic recording and reproducing device which interchangeably uses magnetic tapes having different electromagnetic characteristics.

CONSTITUTION: In a signal circuit system of a deck to be used, the operation is set so as to obtain an optimum recording condition, to a metallic tape when only the potential of a control signal output terminal 1 is high, to a vapor-deposited tape when the potential of both the terminals 1, 2 is high, and also to an oxide tape when that of both the terminals 1, 2 is low. The surface electric resistance value RT of the magnetic tape which is in use is connected to operational amplifiers OP1, OP2, and said setting is executed. The resistance RT is led to a tape kind discriminating circuit 3 consisting of the operational amplifiers OP1, OP2, by the use of component parts which are in contact with the magnetic surface side of a magnetic tape 6, such as tape guides 8, 9 of a tape running mechanism system, and said setting can be executed.