A tester with low signal attenuation and suitable for measuring an electrical characteristic of a subject to be tested includes a circuit board and a first probe. The circuit board has a first surface and a second surface respectively having a first signal transmission line and a second signal transmission line. The first probe has a contact end contacting the subject to be tested and a first signal end and a second signal end respectively connecting the first signal transmission line and the second signal transmission line. The first probe receives a testing signal from the first signal transmission line through the first signal end and transmits the testing signal from the contact end to the subject to be tested, such that the subject to be tested generates a response signal, and the first probe transmits the response signal to the second signal transmission line through the second signal end.