A portable radio terminal testing apparatus has an antenna coupler 20, a connecting member 16, and a measuring device 15. The antenna coupler 20 has a placement member 35, a coupling antenna 25, a pair of through-connection portions, and an impedance transformer 31. The placement member 35 accepts a portable radio terminal 1, which is a testing object, in an unrestricted state. The coupling antenna 25 is disposed so as to be electromagnetically coupled with an antenna 19 of the portable radio terminal 1, and has a pair of antenna elements which are formed at one face side of a dielectric substrate 26 and which have a planar antenna structure of a predetermined shape, and a pair of feeding points, and is formed from a self-complementary antenna having a predetermined impedance within an operating frequency range including at least 800 MHz to 2.5 GHz order.