An exemplary electroencephalogram measurement system includes: a frequency analysis section for, analyzing a frequency power of the electroencephalogram signal of a user with respect to each set of a reference electrode and a measurement electrode an insufficient electrode determination section for, through comparison of the analyzed frequency power against a first threshold value, distinguishing whether a state of attachment of each electrode is sufficient or not and an insufficiency cause estimation section for determining the number of insufficient electrodes distinguished as insufficiently worn, determining a position at which each insufficient electrode is in contact with the user, and estimating a cause for the insufficient state of attachment of the insufficient electrode or electrodes that corresponds to the determined number of insufficient electrodes and position of each insufficient electrode by referring to insufficiency pattern data.
