We conducted small-scale explosion experiments to determine the azimuth angle characteristics of the blast wave from an underground magazine model inside a cover model and discuss its difference in cases with and without a dike model. The magazine comprised a cylindrical steel pipe with one end closed by a fixing jig, and the ratio of the length to the inner diameter was 3. The overpressures of the blast wave were measured using piezoelectric pressure sensors that were placed in twelve locations on the steel plate. The magazine and the cover models were set on a rotary table that changed the azimuth angles of the magazine exit and the pressure sensors between 0 and 180 degrees in intervals of 10 degrees. A series of explosion experiments provided the azimuth angle characteristics of the blast wave from the exit. The increment of the azimuth angle induces a reduction in the peak overpressure. In the present study, we observed two additional phenomena that changed blast wave strength. One was the local geometrical irregularity of the cover model that enhanced the blast wave behind the magazine. The other was the reflection and the diffraction of the blast wave at the dike that enhanced and attenuated the blast wave. We propose an empirical formula that includes the above effects, which can properly estimate the azimuth angle characteristics of a blast wave. The results demonstrate the applicability of the azimuth angle characteristics around an underground magazine.