A metering valve mechanism of an aerosol container in which a stem accommodated in an inner housing is caused to shift from a stationary mode in which the stem is biased by a first elastic member to a propelling mode against the stationary mode to thereby allow the stem to have a contents inflow-side valve action to a metering chamber formation seal valve to cause a shift from a communication state to a closed state of a metering chamber consisting of the inner housing and an outer housing at the outer side thereof and a contents accommodation space region (D, 5) at the upstream side thereof and the contents outflow-side valve action of the stem causes the inner housing and a stem path to shift from the closed state to the communication state, wherein the inner housing consists of: a tube-like section (3a, 3d) that is provided to surround the stem and that sets an inner annular space region as the metering chamber between the inner peripheral surface thereof and the outer peripheral surface of the stem; the outer housing consists of: a sheath-like section that is provided at the outer side of the inner housing and that sets an outer annular space region as the metering chamber between the inner peripheral surface thereof and the outer peripheral surface of the inner housing and an annular ceiling part that has inner and outer communication holes to correspond to the outer annular space region; the outer annular space region consists of: a first face part that receives the pressure action by to-be-propelled contents filled via the stem path and the inner housing and a second face part that receives the pressure action by the propellant at the back side thereof via the inner and outer communication holes; and at least an end of the first face part has an annular piston that has a first inner annular seal section providing the sealing action with the outer peripheral surface of the inner housing and a first outer annular seal section providing the sealing action with the inner peripheral surface of the outer housing, and the seal valve is configured so that: in a contents filling mode in which the contents are filled via the stem path and the inner housing, the seal valve is moved by the strength of 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 (D, 5), characterized in that the annular piston is configured so that an end of the second face part has a second inner annular seal section providing the sealing action with the outer peripheral surface of the inner housing and a second outer annular seal section providing the sealing action with the inner peripheral surface of the outer housing. the inner housing consists of: a tube-like section (3a, 3d) that is provided to surround the stem and that sets an inner annular space region as the metering chamber between the inner peripheral surface thereof and the outer peripheral surface of the stem; the outer housing consists of: a sheath-like section that is provided at the outer side of the inner housing and that sets an outer annular space region as the metering chamber between the inner peripheral surface thereof and the outer peripheral surface of the inner housing and an annular ceiling part that has inner and outer communication holes to correspond to the outer annular space region; a sheath-like section that is provided at the outer side of the inner housing and that sets an outer annular space region as the metering chamber between the inner peripheral surface thereof and the outer peripheral surface of the inner housing and an annular ceiling part that has inner and outer communication holes to correspond to the outer annular space region; the outer annular space region consists of: a first face part that receives the pressure action by to-be-propelled contents filled via the stem path and the inner housing and a second face part that receives the pressure action by the propellant at the back side thereof via the inner and outer communication holes; and at least an end of the first face part has an annular piston that has a first inner annular seal section providing the sealing action with the outer peripheral surface of the inner housing and a first outer annular seal section providing the sealing action with the inner peripheral surface of the outer housing, and the seal valve is configured so that: in a contents filling mode in which the contents are filled via the stem path and the inner housing, the seal valve is moved by the strength of 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 (D, 5), characterized in that in a contents filling mode in which the contents are filled via the stem path and the inner housing, the seal valve is moved by the strength of 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 (D, 5), characterized in that