An adsorption core has (i) a heat medium tube in which a heat medium flows and (ii) an adsorption agent that adsorbs a fluid in a vapor phase outside of the heat medium tube when being cooled by the heat medium and desorbs the absorbed fluid when being heated. The heat medium tube has (i) a core member that is made of metal having a higher hardness with respect to copper and (ii) a covering layer that is made of copper and covers an outer surface of the core member. A sintered body of a copper powder and the adsorption agent is provided in a peripheral portion of the heat medium tube. The copper powder and the heat medium tube are metallically coupled with each other. Accordingly, stiffness of the heat medium tube can be higher while improving a heat transfer performance between the heat medium tube and the adsorption agent.