The present invention relates to a dehumidification and humidification apparatus for vehicles using an adsorbent which is capable of feeding a dehumidified air for preventing fogging of window glass and a humidified air for improvement in comfortableness, and is simplified in construction thereof and reduced in size thereof. The dehumidification and humidification apparatus for vehicles according to the present invention comprises a casing (1), and a blower (2), an adsorbent module (3) and an air passage switching device (4) which are accommodated in the casing. The adsorbent module (3) comprises a Peltier element (30), and a first adsorption component (31) and a second adsorption component (32) which are directly disposed on the respective surfaces of the Peltier element, and the air passage switching device (4) is arranged such that the air passing through the first adsorption component (31) and the air passing through the second adsorption component (32) are each turned toward either a first blowoff port (11) or a second blowoff port (12), and turning directions of the respective airs are switchable therebetween. An electric current flowing through the Peltier element (30) in the adsorbent module (3) is reversed to switch operations of the Peltier element between a heat-absorbing portion and a radiating portion, and switch the turning directions of the respective airs in the air passage switching device (4).