Heat flows emanating from the end mirror cell of the GAMMA 10 tandem mirror during electron cyclotron resonance heating (ECRH) are measured with infrared cameras. From simultaneous measurement of heat flows along and across field lines, 70 % of microwave energy absorbed by electrons is detected as heat losses to in-vessel materials. Nearly equal amount of axial and radial energy losses are observed under the operation of fundamental ECRH only. On the other hand, second harmonic ECRH produces a much larger radial heat flux than fundamental ECRH.