In the Fire Safety Engineering subject, one of the basic phenomena is fire spread on around an object that close to heat source because of the heat transfer process. At high temperature, radiation thermal have a significant effect on an exposed object. There are 3 kinds of characteristic of radiation, which are reflection, absorption, and transmission. Their characteristics are more convenient to learn if there are experiment tools or learning facilities that used radiation to be the main process. Therefore, this research has the objective of designing and built experimental tools used that process and it refers to radiometer. The radiometer is used to study the radiative heat transfer phenomenon in which heat flux emitted from a heat source is measured by using a heat flux sensor as the measurement instruments. Compared to existing radiometer apparatus, the design of this radiometer has some advantages like multiaxis features, user-friendly, portable, and low-cost manufacture. There are some additional features in radiometer likes variation of measurement range in x, y, and z-axis, measurement of view factor, measurement of tilt plane to acknowledge convection effect to heat transfer process, and using flat radiant heater. In this paper, the outcome is the design of a radiometer that can measure heat flux of thermal radiation and suits the study literature.