To provide a flask capable of preventing a specimen from flowing out in case a gas contained in the specimen foams as a result of bumping in the process of vaporizing a solvent from the specimen, or in case microbubbles resulting from the specimen upon adding an emulsifier are accumulated therein.

The flask 1 pertaining to a first embodiment is to be used in a rotary evaporator 30 by attaching it to a rotary holder 33 thereof. The flask 1 is constituted of a mouth 2 that communicates with the inner part of the flask 1 and the outside and is to be attached to the rotary holder 33, a storage section 3 continuing from the mouth 2 and having a bottom member of a diameter greater than that of the mouth 2, and a plurality of baffle plates 5 supported by the inner wall 3c of the storage section 3 and disposed in the direction of baffling the flow of bubbles resulting from the specimen upon vaporizing a solvent therefrom.