Provided are a packaging container, a blood test kit, and a blood analysis method, by which sealability of a collected liquid specimen is made to be compatible with easiness of extraction.Provided is a packaging container including a bag main body portion which has a first surface and a second surface and has an opening portion； and a tongue piece portion which is formed to be continuously extended from the first surface, in which the bag main body portion and the tongue piece portion have an aluminum vapor-deposited layer on an outside thereof, the packaging container further including an adhesion portion which is provided on the second surface to be spaced from the opening portion； and a folded-back portion which is provided between the adhesion portion and the opening portion to fold back the tongue piece portion to the opening portion side, in which the following relational expression is satisfied in a case where a length of the tongue piece portion is a, a length from the opening portion to the folded-back portion is b, and a length from the folded-back portion to the adhesion portion is c. Furthermore, provided are a blood test kit containing this packaging container, and a blood analysis method using this blood test kit.a<；b+c
