An electronic control unit includes: a memory saving a program that has a call/return to/from a function represented as a control flow together with the function itself and a check instruction inserted in a program code of the program for checking whether the program code is executable based on the control flow. The electronic control unit may also include an input unit receiving an input of use frequency information indicative of a use frequency of the function; a measurement unit measuring a load of the electronic control unit; an execution object determiner determining the check instruction to be executed based on the use frequency information and the load; and an arithmetic unit executing the check instruction determined by the execution object determiner at a time of execution of the program.