Multitasking on digital media has a negative effect on mental health and concentration. At the same time, the negative effects of computer usage are not immediately obvious to most people. We suggest that people can improve their daily experience on the computer if they pay closer attention to their multitasking activities. To this end, we have constructed a system that detects multitasking work and periodic negative multitasking routines from computer logs. We created two indicators: relax rate and multitasking rate. The relax rate is defined on the basis of heart rate variability information and the multitasking rate is derived from how often users switch their computer windows. We analyze whether users’ multitasking is negative or not and whether or not negative multitasking is part of a periodic routine. We logged the computer activities and heart rate data of one participant for six days.