A user interface device based on proactive and reactive input quantification, includes a data acquisition unit configured to record input and screen output of a user, an input filtering unit for extracting an input timing for the input of the user, an output filtering unit for extracting an output timing to start a visual change beyond a specific reference for the screen output, an input/output interval extraction unit for generating a distribution of input/output intervals through timings for the input and the screen output of the user, and a model fitting unit for estimating proactiveness and reactiveness by adjusting the distribution of the input/output intervals to a proactive distribution and a reactive distribution.