A detection device having: a terahertz wave generation element; a terahertz wave detection element; a first transmission path arranged upon the terahertz wave generation element; a second transmission path arranged upon the terahertz wave detection element; and a sealed section arranged between the terahertz wave generation element and the terahertz wave detection element and separated from the first transmission path and the second transmission path, so as to surround the first transmission path and the second transmission path. A space between an emission surface in the first transmission path and an incident surface in the second transmission path is connected to a space between the first transmission path and the sealed section and to a space between the second transmission path and the sealed section.