An activity amount calculation device for calculating activity amounts of a resident of a dwelling equipped with a plurality of rooms, the activity amount calculation device comprising: a calculation unit configured to calculate activity amounts of the resident based on detection signals output from a plurality of detection devices that detect the resident when the resident passes through doorways of the plurality of rooms; and a summation unit configured to repeatedly calculate a total activity amount of the resident in a predetermined period by summing the activity amounts calculated by the calculation unit, wherein upon detection of the resident by different detection devices included among the plurality of detection devices, the calculation unit calculates an activity amount of the resident based on a preset relationship between the different detection devices and a reference activity amount and the intensity of exercise calculated based on an elapsed period between detection by one of the different detection devices that has detected first and detection by another of the different detection devices that has detected second and a preset reference period, wherein upon detection of the resident by the different detection devices, the calculation unit uses the reference activity amount obtained from the relationship between the different detection devices and the reference activity amount as the activity amount of the resident when an elapsed period between detection by one of the different detection devices that has detected first and detection by another of the different detection devices that has detected second is longer than or equal to a preset reference period, and uses a product of the reference activity amount obtained from the relationship between the different detection devices and the reference activity amount and a coefficient larger than one as the activity amount of the resident when the elapsed period is shorter than the reference period. a calculation unit configured to calculate activity amounts of the resident based on detection signals output from a plurality of detection devices that detect the resident when the resident passes through doorways of the plurality of rooms; and a summation unit configured to repeatedly calculate a total activity amount of the resident in a predetermined period by summing the activity amounts calculated by the calculation unit, wherein upon detection of the resident by different detection devices included among the plurality of detection devices, the calculation unit calculates an activity amount of the resident based on a preset relationship between the different detection devices and a reference activity amount and the intensity of exercise calculated based on an elapsed period between detection by one of the different detection devices that has detected first and detection by another of the different detection devices that has detected second and a preset reference period, wherein upon detection of the resident by the different detection devices, the calculation unit uses the reference activity amount obtained from the relationship between the different detection devices and the reference activity amount as the activity amount of the resident when an elapsed period between detection by one of the different detection devices that has detected first and detection by another of the different detection devices that has detected second is longer than or equal to a preset reference period, and uses a product of the reference activity amount obtained from the relationship between the different detection devices and the reference activity amount and a coefficient larger than one as the activity amount of the resident when the elapsed period is shorter than the reference period.