To implement an RFID tag reading device that can raise an antenna gain and contribute to miniaturization of the device.

Radiation element 21 includes a linear portion 21a formed in shape of a straight line, and a pair of bent parts 21c, 21c opposed to each other which are bent perpendicularly toward a reflective element 22 respectively from bending points (both ends) 21b, 21b of the linear portion 21a. Each bent part 21c is formed in meandering form in which the part is folded multiple times, and formed in such a manner that at least in a predetermined range from the bending point 21b, the bent part becomes longer as its folded portion is farther away from the linear portion 21a, and from a halfway position thereof, becomes shorter as the folded portion is farther away from the linear portion 21a.