An electrical connecting device having one or more contact members to be in contact with a contact target is provided. The electrical connecting device includes a main body having one or more recesses on a surface thereof opposed to the contact target, and a flexible portion that covers the recesses to form sealed spaces. The main body includes a gas exhaust passage and an air supply passage provided for each of the sealed spaces to adjust a pressure in each of the sealed spaces, and the contact members are respectively disposed to be opposed to the recesses with the flexible portion interposed therebetween.