To provide a heat insulation case for a breast feeding bottle which can be extended and contracted easily by a user, having long lasting heat insulation ability.

The heat insulation case 100 for the breast feeding bottle comprises a housing body 110 for storing the breast feeding bottle 200, and an opening 120 formed on the top side of the housing body through which the breast feeding bottle is inserted. The housing body is composed of an insulation material 110c which includes foam materials, and an approximately cylindrical collapsible part 130 for changing housing capacity which is formed in the lower side of the opening of the housing body, element parts 142a of a fastener part 140 having slider parts 141 arranged in the upper end side and the bottom end side of the collapsible part. One end of both element parts are connected together, forming a stopping part 143 which is undetachable, the stopping part is arranged in approximately central portion between the upper end side and the lower end side of the collapsible part.