There have been many studies on improving intellectual concentration in office. In this study, we named a short break of a few seconds to a few tens of seconds to encourage refreshment ”micro-refresh (MR)” and, as a basis for this study, aimed to confirm by an experiment that the effect of micro-refresh can be measured quantitatively. In the measurement, short breaks of 20 seconds were forcibly given to the experimental participants every 7.5 minutes during the cognitive task as the cognitive task screen turned to all gray, and the difference in intellectual concentration was confirmed using objective indicator “CTR (Concentration Time Ratio)”. In addition, this experiment measured participants’ fatigue and workload through several questionnaires: (1) Progress questionnaire asking about subjective level of concentration and fatigue (2) NASA-TLX asking about mental workload (3) Subjective symptom screening capturing changes in fatigue status over time. As a result, the effect of MR could be quantitatively measured, and it was suggested that MR might reduce subjective fatigue and feeling of sluggishness.