In this study, using a flow path simulating a plate heat exchanger, the local heat transfer coefficients of condensation and evaporation of HFO refrigerants, R32 and CF3I, a candidate additive substance for HFOs were measured, including low mass velocity conditions, which have rarely been done in the past, and their basic characteristics were clarified. The results showed that the evaporation and condensation heat transfer coefficient distributions along the channel width reach a maximum near the heat exchanger inlet/outlet and near the center of the heat exchanger, respectively, and decrease toward the end face of the width direction. The obtained heat transfer coefficient data were also compared with the calculated values based on the existing evaporation/condensation heat transfer correlations. As a result, it was found that the evaporation heat transfer can be reproduced to some extent by the existing correlation, and that the correlation of condensation heat transfer overestimates the measurements, especially in the low flow rate condition.