To provide a heating device capable of efficiently performing heating at an accurate temperature.

In the heating device 10 configured to heat an external heating object through a block member 3 by closely fitting the block member 3 to a heating block 1 with a plurality of built-in cartridge heaters 2 by use of a fixing member 5, an adjustment member 4 having a linear expansion coefficient 4 larger than the linear expansion coefficient 3 of the block member 3 and the linear expansion coefficient 5 of the fixing member 5 is interposed between a major diameter part 5b of the fixing member 5 and the block member 3. Accordingly, when heating from ordinary temperature to a predetermined set temperature, formation of a clearance between the block member 3 and the fixing member 5 due to the thermal expansion difference is compensated by the thermal expansion of the adjustment member 4 to surely maintain the fastening force of the block member 3 to the heating block 1 by the fixing member 5, whereby further uniform and efficient heat transfer from the heating block 1 to the block member 3 is attained.