Abstract: This ground short failure detection device can improve the accuracy of determining a ground short failure. The ground short failure detection device changes the potential of each of two signal lines, and transmits or receives data between a plurality of node devices. The ground short failure detection device comprises: a current measurement unit that measures a current value of a current flowing through each of the two signal lines; a determination unit that determines whether a difference between the measured current values exceeds a predetermined value, and when the difference exceeds the predetermined value, outputs a result indicating that a ground short failure occurs in a low-potential side signal line that has a relatively low potential in a dominant level among the two signal lines; and a control unit that controls the determination unit to determine whether the difference exceeds the predetermined value when a predetermined signal is completely transmitted.