An aerosol dispenser having a metering valve mechanism having a metering chamber and a propellant-accommodating space region configured to be isolated from each other by an annular piston, and a metering formation seal valve configured to isolate the metering chamber from a contents accommodation space region in a propelling mode. In a contents filling mode the seal valve is moved by the flow of the filled contents in a direction away from the stem to allow the filled contents to flow into the contents accommodation space region.