A standard-moisture generator includes a flow controller configured to control a flow of a gas, a dryer connected to the flow controller, configured to absorb water molecules in the gas and to generate a dry gas having a background moisture, a moisture cell connected to the dryer, configured to add an object moisture to the dry gas, and a delay member connected to the moisture cell, configured to pass the dry gas with a delay time depending on a concentration of the background moisture in the dry gas.