PROBLEM TO BE SOLVED: To provide a kit that facilitates uniform mixture and generates carbon dioxide without unevenness for obtaining a foamable skin external preparation of consistent quality regardless of the quality of water used and while saving the time and effort for a user to take measurements.SOLUTION: The present invention provides a kit for obtaining a foamable skin external preparation, characterized in that a first agent is a composition comprising acidic substance and thickener, and a second agent is a composition comprising carbon dioxide generating substance that reacts with the acidic substance to generate carbon dioxide, water and/or humectant.COPYRIGHT: (C)2016,JPO&INPIT