In the present study, we investigate the interaction force between hydrophilic nanospheres immersed in diol-water mixtures using a molecular dynamics simulation with a coarse-grained model. It is found that (i) the diol-water mixtures undergo a liquid-to-liquid phase separation between surfaces, which leads to the formation of a water lens between the surfaces and the accompanying attractive force, and (ii) the full-off force between the surfaces exhibits a peak in the diol-rich region. The simulation results obtained will be discussed in detail, by comparing with those in monohydric alcohol-water mixtures and with the experimental results by an atomic force microscope.