Although conventional antennas have characteristics suitable for mobile radio base stations, their vertical dimension is large, and locations of their installation are limited. A radiator for an first upper antenna 32 is arranged in a hollow nonconductive radome 2, using an internal conductor 7a and a metal pipe 10. A radiator for a second lower antenna 34 is arranged in the radome 2, using metal pipes 14 and 15. Two parasitic elements 31 are installed substantially in parallel with the first antenna 32 below a feeding point 9. Two parasitic elements 33 are installed substantially in parallel with the second antenna 34 above a feeding point 13. These allow the tilt angle to be freely set between -10.degree. and +10.degree. by adjusting the parasitic element length and the antenna to be reduced in size.