To stabilize delay time and to provide a specified frequency range with less dispersion by constituting a delay line by four sheet layers provided with a transmission line and a ground conductor composed of barium oxide and aluminium oxide, etc.

This delay line comprises rectangular sheet layers 16a-16d composed of the barium oxide, the aluminium oxide and silica. Also, on the side face and upper and lower surfaces parts, an input terminal 12, an output terminal 13 and two terminals 14 and 15 for ground are provided. For the sheet layers 16a-16d, the sheet layer 16b where the ground conductor 17 is formed, the sheet layer 16c where the transmission line 18 bent in a meander shape and made to meander is formed and further, the sheet layer 16d where the ground conductor 19 is formed are constituted under a top layer 16a. In this case, by a formula (a light speed Co and a dielectric constant r,) the length A of a line 18 is set so as to turn the frequency (f) of the peak of the delay time to be more than a using frequency range. Thus, the delay time is stabilized and the frequency range with less dispersion is obtained.