PURPOSE: To make a band stop filter smaller-size and lighter-weight than the filter using a coaxial resonator, by using a TM mode resonator to constitute the band stop filter.

CONSTITUTION: A microstrip line 22 corresponding to an eyelet-shaped metallized part 12 is formed in a semicircular notch 21 provided in a box body 2 where two dielectric resonators 1 are stored. Resonators 1 are fitted to holes 23, and the line 22 and the metallized part 12 are connected by a connection ribbon 3. The line 22 and coaxial contact taps 5 and 6 for input and output are connected, and a cover 4 is fitted to the box body 2 and is fixed by screws 7. In this case, the interval between resonators 1 is the 1/4 wavelength. When a power is supplied to the coaxial contacting plug 5 for input, the power is flowed to the line 22 and the connection ribbon 3 to form a magnetic field in the metallized part, and a magnetic field is induced in resonators 1 to couple them by the magnetic field.