This paper reviews recent advancements on application of infrared absorption spectroscopy for analysis of electric field effects of liquid molecules at room temperature. Design of a sample cell for the application of the electric field and the spectroscopic methodology to detect the small change in the IR absorption are explained in detail. Also, we describe the theoretical framework for the analysis of the electric field effects, namely the changes on the orientation and molecular structure, and the signals that originate from the electronic structure. The formulations herein are useful to interpret the changes in the absorbance, the peak position, and the band width of each IR absorption band in the spectrum. Some recent reports will be introduced as the examples that utilize each signal due to the external electric field.