To provide an in-vehicle unit which easily detects a wrong IC card inserted into an ETC in-vehicle unit.

The in-vehicle unit 10 is provided with: a flag storage part 14a which stores a flag set when a vehicle enters a toll road through an entrance toll gate and reset when the vehicle leaves the toll gate through an exit toll gate; an ID reading part 13 which reads an ID of an IC card 20 mounted on the in-vehicle unit 10; an ID storage part 14c which stores the ID of the IC card 20 read by the ID reading part 13 when the flag is set and cancels the stored ID when the flag is reset; an IC comparison part 15 which compares the ID of the IC card 20 read by the ID reading part 13 with the ID of the IC card 20 stored in the ID storage part 14c when power is supplied or when the IC card 20 is newly inserted; and alarm parts 16, 17 for giving an alarm when mismatch is detected by the ID comparison part 15.