In the present study an objective method for evaluating work-related painfulness at a pectoral limb ( that is an upper limb of human body ) was derived from combining biomechanical and physiological evaluations. Flexions and extensions about an elbow joint with a tool in a hand were taken up for the work models with a pectoral limb. Experiments of the model works at five different positions were carried out by ten male subjects in order to evaluate physical and physiological burdens. On the basis of the experimental results an objective index of painfulness was defined as proportional to the magnitude of the physical load and inversely proportional to the level of the skin blood flow. And it was confirmed that the index of painfulness agreed well with the subjective evaluations.