An adsorber comprising: a closed container (101, 201) in which an adsorption medium is included; an adsorption part (102, 202) that is provided in the closed container (101, 201) and includes an adsorbent, which adsorbs and desorbs the adsorption medium; and an evaporation/condensation part (103, 203) that is provided in the closed container (101, 201) and that exchanges heat between the adsorption medium and a heat exchanging medium, which is supplied from outside of the closed container (101, 201), to evaporate and condense the adsorption medium, wherein: the evaporation/condensation part (103, 203) includes a heat transfer part (103b, 203b) that transfers heat of the heat exchanging medium to the adsorption medium; the heat transfer part (103b, 203b) is capable of holding the adsorption medium; the amount of adsorption medium held by the heat transfer part (103b, 203b) is not more than an amount with a maximum adsorption capacity of the adsorption medium which can be adsorbed by the adsorbent of the adsorption part (102, 202); and the heat transfer part (103b, 203b) is a porous heat transfer body; characterized in that a clearance corresponding diameter of the heat transfer part (103b, 203b) is within a range from 7 to 260 μm, and is expressed by a mathematical formula 1: clearance corresponding diameter = d · 3 π / 4 1 − Φ − 1, where: d is a line diameter or a framework diameter of the porous heat transfer body; and Φ is a porosity of the porous heat transfer body. a closed container (101, 201) in which an adsorption medium is included; an adsorption part (102, 202) that is provided in the closed container (101, 201) and includes an adsorbent, which adsorbs and desorbs the adsorption medium; and an evaporation/condensation part (103, 203) that is provided in the closed container (101, 201) and that exchanges heat between the adsorption medium and a heat exchanging medium, which is supplied from outside of the closed container (101, 201), to evaporate and condense the adsorption medium, wherein: the evaporation/condensation part (103, 203) includes a heat transfer part (103b, 203b) that transfers heat of the heat exchanging medium to the adsorption medium; the heat transfer part (103b, 203b) is capable of holding the adsorption medium; the amount of adsorption medium held by the heat transfer part (103b, 203b) is not more than an amount with a maximum adsorption capacity of the adsorption medium which can be adsorbed by the adsorbent of the adsorption part (102, 202); and the heat transfer part (103b, 203b) is a porous heat transfer body; characterized in that a clearance corresponding diameter of the heat transfer part (103b, 203b) is within a range from 7 to 260 μm, and is expressed by a mathematical formula 1: clearance corresponding diameter = d · 3 π / 4 1 − Φ − 1, where: d is a line diameter or a framework diameter of the porous heat transfer body; and Φ is a porosity of the porous heat transfer body. the evaporation/condensation part (103, 203) includes a heat transfer part (103b, 203b) that transfers heat of the heat exchanging medium to the adsorption medium; the heat transfer part (103b, 203b) is capable of holding the adsorption medium; the amount of adsorption medium held by the heat transfer part (103b, 203b) is not more than an amount with a maximum adsorption capacity of the adsorption medium which can be adsorbed by the adsorbent of the adsorption part (102, 202); and the heat transfer part (103b, 203b) is a porous heat transfer body; characterized in that a clearance corresponding diameter of the heat transfer part (103b, 203b) is within a range from 7 to 260 μm, and is expressed by a mathematical formula 1: clearance corresponding diameter = d · 3 π / 4 1 − Φ − 1, where: d is a line diameter or a framework diameter of the porous heat transfer body; and Φ is a porosity of the porous heat transfer body. d is a line diameter or a framework diameter of the porous heat transfer body; and Φ is a porosity of the porous heat transfer body.