PURPOSE: To detect the splicing part of a tape surely by comparing the output voltage from a photodetecting part and the voltage obtained by phase inversion of the output voltage from the photodetecting part with a reference voltage.

CONSTITUTION: When a voltage is outputted upon arrival of the splicing part 442 of a tape 44 at the position facing an LED D16, said voltage does not exceed a reference voltage in an operational amplifier OP4; therefore, no output is generated from the amplifier OP4. Whereas, the change in the voltage is inverted of phase by an operational amplifier OP5. Then the point where said voltage exceeds the reference voltage exists in an operational amplifier OP6; therefore the detection signal of an L level is generated in the end and the part 442 is surely detected.