The purpose of this research is the observation of cell reactions by an electromagnetic wave. We study the microwave applicator for in vitro research and examine the device with simulation to decide the optimum condition. The simulation with Finite Difference Time Domain (FDTD) method has an assumption that Cell Biology Experiment Facility (CBEF) is attached to the bottom of waveguide which is sealed with a metal plate and the waves enter from the other open side. This report shows the Specific Absorption Rate (SAR) of cell and electric field intensity in the facility. We also propose the exposure system which can irradiate living cells with the microwave efficiently.