Provided is an electronic control unit including: a master microcomputer having a master memory (23) that includes a master target data area (A7), a plurality of transmission master banks (A2, A3), a transmission master information area (A1), a reception slave information area (A4) and a plurality of reception slave banks (A5, A6); and a slave microcomputer having a slave memory (33) that includes a slave target data area (B7), a plurality of transmission slave banks (B5, B6), a transmission slave information area (B4), a reception master information area (B1) and a plurality of reception master banks (B2, B3).