In a dehumidification/humidification device, a blower and an adsorbent module are contained in a casing. In other embodiment, the blower, the adsorbent module, and a flow passage-changing device are contained in the casing. The adsorbent module includes an adsorbing element formed by carrying an adsorbent on a permeable element and a heater directly disposed on the adsorbing element. The state of the electrification of the heater is changed and an air-blowing direction or a flow passage is changed, whereby a dehumidified air is discharged from a first suction/discharge port (or discharge port), and a humidified air is discharged from a second suction/discharge port (or discharge port).