A diagnosis system includes: a charging control part that controls, upon connection between a vehicle and a charger provided at an outside of the vehicle, charging from the charger to a secondary battery provided on the vehicle; and a derivation part that derives a degradation degree of the secondary battery based on a change amount of a charging rate of the secondary battery and an integration value of a charging current of the secondary battery, wherein the charging control part determines, based on a remaining time until a next departure time of the vehicle, whether specific charging in which a charging pause period is provided in a middle of a charging time of the secondary battery is performed.