This study was conducted to investigate the effect of natural mineral complex fed to laying hens during the summer in terms of the egg quality. A total of 480 laying hens (160 leghorns, 160 Korean native chickens and 160 silkies, all 62 weeks old), were used for 4 weeks. The four dietary treatments were as follows: CON) basal diet; MC1) CON + 0.1% natural mineral complex (NMC); NMC3) CON + 0.3% NMC, and NMC5) CON + 0.5% NMC. In terms of egg weight, the NMC3 and NMC5 treatments had significantly higher egg weights than that of the CON (p < 0.001) in all species. Eggshell strength in the NMC3 and NMC5 treatments was significantly higher than that of the CON in the leghorns on 2 week (p < 0.01). In the Korean native chickens, the eggshell strength for the NMC1, NMC3 and NMC5 treatments was significantly higher than that of the CON during all periods. In 4 week, the eggshell strength for the CON and NMC1 treatment was significantly higher in the leghorns (p< 0.001), but the MC treatments had a significantly higher eggshell strength than that of the CON in Korean native chickens. Egg production was significantly improved in all the treatments compared to the NMC3 treatment (p < 0.05), and hatchability was also improved compared to the CON (p < 0.05). In conclusion, supplementation of natural mineral complex in chicken diets influenced the egg quality during the summer season.