A transformation device installed in a vehicle includes a transformation section, a transmission section, a detection section and a control section. The transformation section transforms data transmitted from a first control device in a first communication protocol to data in a second communication protocol. The transmission section transmits the data transformed by the transformation section to a second control device. The detection section detects an update of one or more of the first control device and the second control device. In a case in which an update of at least one of the first control device or the second control device is detected by the detection section, the control section changes a mode of transformation by the transformation section.