Abstract: A conversion device includes: a unit attribute update unit that specifies a unit associated with a representative value approximating a feature vector for a biological signal, and updates a representative value and energy of the specified unit; a unit update unit that, when a plurality of feature vectors outside a predetermined range of a representative value of a unit of the unit data are acquired within a predetermined time, adds data for a new unit identifier to unit data; a class update unit that, when there is no class including a unit having energy within a predetermined range of energy of the new unit, adds data for a new class identifier to class data; and a motion update unit that updates motion data by associating, with an identifier of a class acquired after updating the class data, an identifier of a motion corresponding to the class.