The flow and heat/mass transfer characteristics of falling film of LiBr-H₂O solution over a horizontal tube with water vapor absorption were examined experimentally. Variables are the solution flow rate and temperature at the top of the tube, and the absorber pressure. The liquid film wave become wavy with the higher absorption rate. The range of wave formation becomes larger with the lower solution flow rate and the higher absorber pressure. The origin of the wave formation is considered to be the Marangoni effect, which is to be studied in detail as a future work.