A study was made on crack developments of the nearly building due to rock blasting for road construction at the 623 Common Block near the rear side of the Gamchun Habor. The gelogy of the study area is composed of andesite, which belongs to the Kyungsang System of the Cretaceous Period. For 3 months of blasting events, the vibration velocity data were measured at the site just in front of the K freezing factory. The data were divided into 4 groups according to the period of blasting(i.e, DATA 1, DATA 2, DATA 3 and DATA 4), for deriving K and n values. As a result, DATA 1 shows that K and n were 83.3756 and -0.848, respectively, and then K and n were progressively increased in absolute values for the follow-up groups and the last DATA 4 shows K and n were 2980.4898 and -1.502, respectively. Such differences in K and n values may be due to partly : 1) variations geological characteristics, from the upper rather weathered, fisssuring soft rocks at the earlier stage less weathered and fissuring hard rocks at the later stage of blasting events, and 2) the geometry between the blasting and detecting points.Among the total count of 225 blasting events, the number exceeding the safety limits of 0.5cm/sec was 20(8.9% of the total), the maximum displacement detected at the crack gage was 0.25mm, the level of which is far less to cause the occurrence and development of any cracks to the K factory. Therefore, it was confirmed that there were no damages such as structural failure or safety problem to the building.