1. A will-expression modeling device simulating human will-expression responding to an direction input given from the outside, comprising: a computer; an interest interpretation section, implemented on the computer, that collates said direction input with a predetermined hedonic interest relationship table and outputs a mood factor representing pleasure/displeasure; an emotion creating section, implemented on the computer, that prepares a plurality of emotional states obtained by modeling human emotions and causes state transitions to occur in the emotional states according to said mood factor to simulate a change in human emotion responding to said direction input; and a will-expression section, implemented on the computer, that prepares in advance a plurality of mental-will states obtained by modeling human will and selects a new mental-will state from said emotional states or a combination of a mental-will state and an emotional state, wherein when receiving an instruction input of encouragement or suppression based on a relationship between said direction input and said mental-will states being selected from an outside instructor, said interpretation section redefines said hedonic interest relationship table in response to said instruction input to make said will-expression closer to human common sense and super-ego.