A sprayer designed usable in both erect and inverted states and a pump mechanism therefor, comprising a pressure chamber consisting of a cylinder and a piston, a pair of check valves provided in opposition to each other below said pressure chamber, a liquid inlet hole allowing flow of the liquid in the liquid container from its neck side portion into said pressure chamber when the sprayer is brought to its inverted position, and a skirt member adapted to inhibit leakage of the liquid to the spray head from said liquid inlet hole when the sprayer is in its inverted position. Inflow of the liquid and air into the pressure chamber is perfectly inhibited by the two check valves when the sprayer is either in its erect position or in its inverted position.