Monitoring system and monitoring method

A monitoring method comprising:

• by a thermal image acquisitor attached to a wall or a ceiling on a side of a head of a care recipient in a case where the care recipient lies on a bed, capturing an image of the bed and its surroundings from diagonally above to acquire a thermal image;
• setting two reference lines respectively corresponding to a left end and a right end of the bed in the thermal image, and a reference height for determining sitting-up of the care recipient, by reference setting circuitry;
• detecting a mass of a heat source in the thermal image by heat source detection circuitry;
• determining a state of the care recipient from a positional relationship between a safe area enclosed with the reference lines and the reference height and the mass of the heat source by state determination circuitry;
• and
• outputting a determination result of the state determination circuitry by a determination result output device.