A water-based paint includes a fine powder composition which includes fine powdery clay minerals comprising pyrophyllite and sepiolite, a fine powdery thixotropy support agent containing hydroxypropyl methylcellulose and comprising first and second agents having 2 percent by weight aqueous solution viscosities at 20° C. of 2400 mPa·S to 4500 mPa·S and 64000 mPa·S to 90000 mPa·S, respectively, and a fine powdery inorganic porous material comprising diatomaceous earth and zeolite. A thixotropic index when the fine powder composition is dispersed and dissolved in water is 3.0 to 4.0. The thixotropy support agent includes 67 to 91 percent by weight of the first agent and 9 to 33 percent by weight of the second agent.