The ligation reaction is widely used in molecular biology. There are several kits available that complete the ligation reaction very rapidly but they are rather expensive. In this study, we successfully modified the ligation buffer with much lower cost than existing kits. The ligation reaction can be completed in 10 min using very low activities such as 0.01 U T4 DNA ligase, and costs only $1 for 100 reactions of 20 mu l scale. We name this ligation system the "Coffee Break Ligation" system; one can complete ligation reaction while drinking a cup of coffee, and perform 100 reactions by spending money equivalent to a cup of coffee.