To provide a transmission device for electric vehicles, which can prevent deterioration in the transmission quality due to the reflection of a high-frequency electrical signal and deformation of waveform, even if vehicles in the same short organized group are changed freely and can perform normal and high-reliability high-speed transmission.

In a transmission device for electric vehicles, a trunk transmission line by electrical signals of high frequency is connected by a transmission port in connecting trains which are constituted of a plurality of vehicles and have driver's seats at both head vehicles. The device is provided with two transmission ports 16a and 16b arranged in the connection parts of the head vehicles which connect the trains, and a connection switching means 21 for connecting the transmission ports of the same side of the two transmission ports 16a and 16b, in connecting the trains.