A delivery server includes: an update unit configured to update a remaining gas amount on a basis of a gas usage obtained based on comparison between a plurality of sets of meter indication data when receiving a set of meter indication data, included in the plurality of sets of meter indication data, of a gas meter configured to detect the gas usage in a gas cylinder; a prediction unit configured to predict a prospective remaining gas amount on a basis of a change in a past gas usage obtained based on comparison between the past gas usages consumed in the gas cylinder; and a determination unit configured to determine a date on which the predicted remaining gas amount reaches a predetermined value as a delivery date of the gas cylinder.