The omnidirectional antenna of the present invention comprises a dielectric core 20 of ceramic material which has a longitudinal hole 21 formed in the center; a strip line 30 which is bent to fit the circumference of the dielectric core 20 by a press-forming method and is covered over the upper outer circumference of the dielectric core; a lower cap 40 which is inserted over the bottom end of the dielectric core and has a hole formed at the center of the bottom; a feeder 50 which is passed through and inserted from down to up into the holes formed in the bottom cap and the dielectric core and the top end of which is connected with the strip line 30 on the upper surface of the dielectric core; and a strip line fixing means 60 for combining the lower cap and strip line to the dielectric core.