Recently, the development of high temperature heat pump systems for heat recovery from industrial waste heat below 100 °C is one of important subjects to reduce primary energy consumption. However, in order to develop such systems, it is indispensable to use an environmentally acceptable refrigerant, highly efficient heat exchangers and highly efficient compressors. From this viewpoint, in the present study, the condensation of low GWP refrigerant R1234ze(Z) in vertical channels is investigated experimentally in order to establish optimum design method of plate-fin heat exchanger. Then, heat transfer coefficients are measured by two type cooling methods. One type is one side cooling method, another type is both cooling method. As the results, the heat transfer coefficient in consideration of fin efficiency of one side cooling method is higher than that of both cooling method in high quality.