The speech sound intelligibility assessment system includes: an output section for presenting a speech sound to a user a biological signal measurement section for measuring an electroencephalogram signal of the user a positive component determination section for determining presence/absence of a positive component of an event-related potential in the electroencephalogram signal in a zone from 600 ms to 800 ms from a starting point, which is a point in time at which the output section presents a speech sound a negative component determination section for determining presence/absence of a negative component of an event-related potential in the electroencephalogram signal in a zone from 100 ms to 300 ms from the same starting point and an assessment section for evaluating whether the user has clearly aurally comprehended the presented speech sound or not based on the results of determination of presence/absence of the positive and negative components, respectively.
