Effect of B₂O₃ content on crack resistance was investigated by indentation tests of glass samples with various compositions of B₂O₃. The ternary SiO₂–B₂O₃–Na₂O glass system (SBN series) and non-alkaline aluminoborosilicate glass system (SAB series). When B₂O₃ is substituted with SiO₂ in the SBN system (“SBN1” series), crack resistance has a relationship with density. In a series of the SBN system where density did not change with B₂O₃ content (“SBN2” series), crack resistance decreased with increasing B₂O₃ content. On the other hand, crack resistance increased with increasing B₂O₃ content in the SAB series, where density did not change. According to the results of NMR measurement, boron in 4-cordination state (^[4]B) increased in the SBN2 series while boron in 3-cordination state (^[3]B) increased in the SAB series with increasing B₂O₃ content. Therefore, crack resistance increases with increasing ^[3]B and decreases with increasing ^[4]B. The difference in structure between ^[3]B and ^[4]B containing glasses leads to different effect on residual stress around the indentation, resulting in difference in crack resistance.