A quasi-experimental design was adopted to investigate the effect of integrating technology into mathematics teaching on students' number sense and their learning attitudes. Two sixth-grade classes were selected from an elementary school in Taiwan for participation in this study. The control group with 32 students followed their usual mathematics instruction on number sense without using technology. The experimental group with 32 students learned number sense in a technology-based environment. The ANCOVA results showed a statistically significant difference between the control group and the experimental group on number sense performance. The "t"- test results showed no significant difference before and after the instruction for the control group. However, there was a statistically significant difference before and after the instruction for the experimental group. Furthermore, data also showed a significant difference in the students' learning attitudes between the control group and the experimental group after the teaching. These results indicated that integrating technology into number sense teaching and learning not only promote students' number sense, but also has a positive effect on attitudes towards learning number sense. (Contains 5 tables and 6 figures.)