A vehicular arithmetic operation processing device that is mounted in a vehicle having a communication function of communicating with an outside of the vehicle and the vehicular arithmetic operation processing device includes an electronic control unit. The electronic control unit is configured to: perform an arithmetic operation for an arithmetic operation task, output a result of the arithmetic operation, and receive an arithmetic operation task from the outside of the vehicle by using the communication function when an amount of arithmetic operations performed in the vehicular arithmetic operation processing device is equal to or less than a predetermined first value; and transmit an arithmetic operation task to the outside of the vehicle by using the communication function when the amount of arithmetic operations which are performed in the vehicular arithmetic operation processing device is equal to or greater than a predetermined second value.