The inter-CPU data transfer device is used for an electronic control apparatus which includes a first CPU having a first memory and a second CPU having a second memory, the first CPU periodically performing a data-updating process to update a plurality data items stored in the first memory, the second CPU performing a data-referring process in which the plurality of the data items updated by the first CPU are referred to for computation purpose. The inter-CPU data transfer device further includes a data transfer memory, a first data transfer section activated in order to write the plurality of the data items written in the first memory to the data transfer memory when the first CPU starts the data updating process, and a second data transfer section writing the plurality of the data items written in the data transfer memory to the second memory when the second data transfer section detects that the second CPU is not performing the data-referring process.