In recent years, long work hours and overtime work have become a social problem in Japan. Therefore, attention is focused on improving the work style in Japan. In particular, there is a demand for improving the efficiency of desk work. In this paper, we aim to clarify the relationship between work and concentration, and the influence of interruptions on the concentration state and the number of working hours (work time) to realize appropriate time allocation in desk work. In the experiment, staff members of the Toyama prefectural office were recruited as subjects to obtain data on the work times and concentration state. We use a device called Spire to determine the concentration state. Spire can acquire respiration information. As a result, it was found to be necessary to continue work for 10 min or more in order to achieve high concentration and work efficiency. However, it was found that if concentration was not attained within 10 min from the start of work, it was necessary to interrupt the work. It was also found that interruption did not affect the work time or concentration state.