In a signal transmission device, first open-ended resonators include a first first-open-ended resonator and a second first-open-ended resonator, in which open ends of the first first-open-ended resonator face a central portion of the second first-open-ended resonator, and a central portion of the first first-open-ended resonator faces open ends of the second first-open-ended resonator. When second open-ended resonators are employed, the second open-ended resonators include a first second-open-ended resonator and a second second-open-ended resonator, in which open ends of the first second-open-ended resonator face a central portion of the second second-open-ended resonator, and a central portion of the first second-open-ended resonator faces open ends of the second second-open-ended resonator. The first and the second open-ended resonators in closest proximity to each other in the first resonator are arranged such that the respective open ends thereof face each other and the respective central portions thereof face each other.