A method for manufacturing a multi-chamber container (100) including a medicine storage chamber (61) and a chemical solution storage chamber (62) separated by a weak seal portion (30), wherein the sides (11A, 12A) are joined together. 1st sheet-like member (10) containing 1 chemical medical agent storage chamber formation part (11) and 1st chemical medical solution storage chamber formation part (12), and the 2nd chemical medical agent storage chamber formation part by which one side (21A, 22A) was joined (21) and the step of preparing the second sheet-like member (20) including the second chemical liquid storage chamber forming portion (22), and the first sheet-like member (10) and the second sheet-like member (20) are joined. Forming a medicine storage chamber (61) and a chemical solution storage chamber (62). The weak seal part (30) is formed by joining one side (12A) of the first chemical liquid storage chamber forming part (12) and one side (22A) of the second chemical liquid storage chamber forming part (22).弱シール部（３０）によって分離された薬剤収容室（６１）および薬液収容室（６２）を含む複室容器（１００）の製造方法であって、一辺（１１Ａ，１２Ａ）同士が接合された第１薬剤収容室形成部（１１）および第１薬液収容室形成部（１２）を含む第１シート状部材（１０）、ならびに一辺（２１Ａ，２２Ａ）同士が接合された第２薬剤収容室形成部（２１）および第２薬液収容室形成部（２２）を含む第２シート状部材（２０）を準備する工程と、第１シート状部材（１０）および第２シート状部材（２０）を接合することによって薬剤収容室（６１）および薬液収容室（６２）を形成する工程と、を備える。弱シール部（３０）は、第１薬液収容室形成部（１２）の一辺（１２Ａ）および第２薬液収容室形成部（２２）の一辺（２２Ａ）同士が接合されることによって形成される。
