A heating unit includes: a base having an upper surface; a first heating element buried in an upper part of the base, the upper part including the upper surface, the first heating element having a flat shape almost parallel to the upper surface; and a second heating element buried in a lower part of the base and arranged in a location lower than the first heating element with respect to the upper surface, the lower part being joined to the upper part, and the second heating element having a flat shape. First and second projection patterns have an overlapping portion where the first projection pattern and the second projection pattern partially overlap each other, the first projection pattern representing the first heating element projected on the upper surface of the base, and the second projection pattern representing the second heating element projected the upper surface of the base.