1. A working skill estimating program for estimating working skills of an agent based on response records collected during a predetermined period, each response record containing information about an inquiry from a customer, a response thereto, and time spent therefor, the program making a computer function as: large category classifying means for classifying the response records into large categories according to predetermined classification rules based on topics of inquiries and responses; small category generating means for generating small categories by further classifying the response records belonging to each of the large categories according to a predetermined definition of similarity between individual response records; disturbance distinguishing means for distinguishing whether the response records belonging to each of the small categories generated by the small category generating means are construed to be common response records that are produced constantly over time or disturbances whose frequency exhibits a significant time dependency; and skill estimating means for estimating working skills of the agent in each of the large categories by using the common response records identified by the disturbance distinguishing means.