A particulate matter detecting device includes: an element unit on which particulate matter contained in exhaust gas from an internal combustion engine is deposited; a heater that heats the element unit; a detecting unit that detects the amount of particulate matter on the basis of electrical characteristics of the element unit; and a control unit that controls the operation of the heater. For a predetermined period that does not include a period in which the particulate matter is deposited on the element unit, the control unit operates the heater using a predetermined amount of control set in advance such that the temperature of the element unit is higher than the temperature of the exhaust gas and lower than a predetermined temperature at which the element unit is thermally degraded.