During a driving activity of an automobile, a work characteristic evaluating apparatus is provided for judging a factor (a physical work load or a mental load) of stress that a work activity places on the worker to evaluate a work characteristic. The work characteristic evaluating apparatus 1 comprises a masseter muscle myoelectric potential acqusition device 10 which measures and acquires myoelectric potential of a masseter muscle which moves independently of the driving activity of the driver, a work intensity acquisition device 20 which measures and acquires steering torque around the steering shaft as a work intensity of steering activity, a correlation calculating module 38 which computes a correlation between time-series data of the myoelectric potential of the masseter muscle and time-series data of the steering torque, and a judgment module 39 which judges whether the stress placed on the worker is caused by a physical work load or a mental load based on the correlation coefficient.