When two targets are presented in a rapid succession, correct identification of the first target results in detection deficit for the second target because of effects of visual attention. In the present study we measured temporal effects of visual attention with increment luminance thresholds of a second target. We also obtained that temporal effects of visual attention were influenced by difficulty of a first attention task. The results showed that detection sensitivity of the second target in the double-task condition decreased up to about 500 ms when the first target was accurately detected. It was also shown that when the first task was easier detection sensitivity of the second target was recovered more rapidly.