An anaerobic threshold estimation method comprising: a first acquisition step of acquiring by a heart rate acquisition unit of a biological information acquisition unit a heart rate of a target person during a period from a time when the target person starts exercise wherein exercise intensity gradually increases to a time when the exercise intensity becomes 90% from a biological sensor attached to the target person externally and having functions of a heart rate meter and an electrocardiograph; a second acquisition step of acquiring by the biological information acquisition unit an electrocardiographic waveform of the target person during the period; a third acquisition step of acquiring by a feature amount acquisition unit of the biological information acquisition unit a predetermined feature amount from the acquired electrocardiographic waveform, the predetermined feature amount being a height of a T wave included in the electrocardiographic waveform, the height of the T wave included in the electrocardiographic waveform × a heart rate, or a height of an R wave included in the electrocardiographic waveform; and an estimation step of estimating by an estimation unit an anaerobic threshold of the target person based on a relationship between the predetermined feature amount and an exercise intensity calculated from the heart rate by a Karvonen method, wherein the estimation step includes: a step of obtaining by an inflection point processing unit of the estimation unit the relationship, extracting an inflection point in a change of the predetermined feature amount with respect to the exercise intensity, only within a range of 50% to 90% of the value of exercise intensity, and obtaining exercise intensity at the inflection point; and a step of calculating by an anaerobic threshold calculation unit of the estimation unit the exercise intensity at the inflection point as the anaerobic threshold of the target person. a first acquisition step of acquiring by a heart rate acquisition unit of a biological information acquisition unit a heart rate of a target person during a period from a time when the target person starts exercise wherein exercise intensity gradually increases to a time when the exercise intensity becomes 90% from a biological sensor attached to the target person externally and having functions of a heart rate meter and an electrocardiograph; a second acquisition step of acquiring by the biological information acquisition unit an electrocardiographic waveform of the target person during the period; a third acquisition step of acquiring by a feature amount acquisition unit of the biological information acquisition unit a predetermined feature amount from the acquired electrocardiographic waveform, the predetermined feature amount being a height of a T wave included in the electrocardiographic waveform, the height of the T wave included in the electrocardiographic waveform × a heart rate, or a height of an R wave included in the electrocardiographic waveform; and an estimation step of estimating by an estimation unit an anaerobic threshold of the target person based on a relationship between the predetermined feature amount and an exercise intensity calculated from the heart rate by a Karvonen method, wherein the estimation step includes: a step of obtaining by an inflection point processing unit of the estimation unit the relationship, extracting an inflection point in a change of the predetermined feature amount with respect to the exercise intensity, only within a range of 50% to 90% of the value of exercise intensity, and obtaining exercise intensity at the inflection point; and a step of calculating by an anaerobic threshold calculation unit of the estimation unit the exercise intensity at the inflection point as the anaerobic threshold of the target person. a step of obtaining by an inflection point processing unit of the estimation unit the relationship, extracting an inflection point in a change of the predetermined feature amount with respect to the exercise intensity, only within a range of 50% to 90% of the value of exercise intensity, and obtaining exercise intensity at the inflection point; and a step of calculating by an anaerobic threshold calculation unit of the estimation unit the exercise intensity at the inflection point as the anaerobic threshold of the target person.