[en] We report the first detection of a gap and a ring in 336 GHz dust continuum emission from the protoplanetary disk around TW Hya, using the Atacama Large Millimeter/Submillimeter Array (ALMA). The gap and ring are located at around 25 and 41 au from the central star, respectively, and are associated with the CO snow line at ∼30 au. The gap has a radial width of less than 15 au and a mass deficit of more than 23%, taking into account that the observations are limited to an angular resolution of ∼15 au. In addition, the ¹³CO and C¹⁸O $J=3-<!--\; ???\; -->2$ lines show a decrement in CO line emission throughout the disk, down to ∼10 au, indicating a freeze-out of gas-phase CO onto grain surfaces and possible subsequent surface reactions to form larger molecules. The observed gap could be caused by gravitational interaction between the disk gas and a planet with a mass less than super-Neptune (2$M_{\mathrm{N}\mathrm{e}\mathrm{p}\mathrm{t}\mathrm{u}\mathrm{n}\mathrm{e}}$), or could be the result of the destruction of large dust aggregates due to the sintering of CO ice.