A hearing-aid gain determination system (100) is provided with the following: a biosignal measurement unit (50) that measures a brain-wave signal from a user a sound-stimuli determination unit (70) that determines the frequencies of sound stimuli including a first sound, a second sound, and a third sound, which are pure tones a sound-pressure determination unit (71) that determines the sound pressures of the first sound, the second sound, and the third sound such that each is less than or equal to a prescribed threshold, the sound pressure of the second sound is less than that of the first sound, and the sound pressure of the third sound is less than that of the second sound an output unit (10) that presents the first sound, the second sound, and the third sound to the user using the frequencies and sound pressures determined by the sound-stimuli determination unit and the sound-pressure determination unit a feature-quantity extraction unit (55) that extracts feature quantities relating to time/frequency information for event-related electric potentials falling within prescribed time periods after the presentation of each of the aforementioned sounds and a gain determination unit (65) that, referring to prescribed benchmarks, determines a hearing-aid gain for each of the frequencies of the sound stimuli on the basis of the feature quantities extracted by the feature-quantity extraction unit.Linvention concerne un système de détermination de gain de prothèse auditive (100) comprenant : une unité de mesure de biosignal (50) qui mesure un signal donde cérébrale provenant dun utilisateur une unité de détermination de stimuli sonores (70) qui détermine les fréquences de stimuli sonores comprenant un premier son, un deuxième son et un troisième son, qui sont des tons purs une unité de détermination de pressions sonores (71) qui détermine les pressions sonores du premier son, du deuxième son et du troisième son de sorte quelles soient inférieures ou égales à un seuil pre
