A thermal developing apparatus for thermally developing a latent image formed on a thermal developing recording material by a thermal developing portion, the apparatus comprising: a heating unit that heats the thermal developing recording material carried to the thermal developing portion, the heating unit comprising a plurality of heating portions that are aligned in a direction that intersects orthogonally with a carrying direction of the thermal developing recording material; and a plurality of temperature measuring portions that measure temperatures of the plurality of heating portions respectively, each of said plurality of temperature measuring portions being arranged to measure a center portion of a temperature distribution in each of said plurality of heating portions.