PROBLEM TO BE SOLVED: To provide a device capable of estimating a mental load attributed to an operation of on-vehicle information equipment.SOLUTION: A respiration rate is derived based on respiratory data acquired from a respiration detection sensor (S330), and an SCL (skin conductance level) is derived based on skin conductance data acquired from a skin conductance detection sensor (S340). All respiration rates and SCLs associated with the corresponding time are acquired in an operation period (S370), and a representative value of the respiration rates in the period and a representative value of the SCLs in the period are calculated (S380). The sum of the representative value of the respiration rates in the period and the representative value of the SCLs in the period is calculated as an evaluation index (S390), and if the difference between the evaluation index and an evaluation criterion is equal to or greater than a specified value, a mental load attributed to an operation of on-vehicle information equipment is evaluated as being felt by a driver while an automobile is driven (S400).
