Apparatus for measuring transpiration amount

Described is an apparatus for measuring a water transpiration amount, which comprises a barrel-type body having a humidity sensor inside of the body and opening portions on the top and bottom of the body, wherein a gas introductory path for feeding, from the outside of the apparatus, a gas having a predetermined water content to a surface to be measured is disposed at the side wall portion of the body and a freely openable or closable shutter is installed at the bottom opening portion of the body.The apparatus according to the present invention makes it possible to carry out accurate and prompt measurement of a water amount transpired locally from the skin surface, ocular surface or the like without being influenced by the external circumstances such as wind.