According to the present disclosure, a remaining amount estimation method for a hydrogen tank used in a fuel cell device including at least one fuel cell unit includes the step of estimating a time when the remaining amount of hydrogen in a hydrogen tank falls to a first threshold value or below based on a used amount of hydrogen in the hydrogen tank during a first time period of a plurality of consecutive days and the step of notifying a display device of the time. When a used amount of hydrogen in the hydrogen tank during a second time period of a plurality of consecutive days within the first time period is less than or equal to a second threshold value, the time is estimated based on a used amount of hydrogen in the hydrogen tank during the first time period excluding the second time period.
