In a decision making process, the ambiguity of qualitative probabilistic expressions may result in a wrong conclusion. For this reason there had been many studies of quantifying qualitative probabilistic expressions in English-speaking countries. In this research, quantification of Korean qualitative probabilistic expressions is conducted through 4-step questionnaires. The numerical data of 78 verbal phrases were collected in the first questionnaire and classified in two categories (i.e., uncertainty and frequency). In each category, qualitative probabilistic expressions were divided into eleven groups according to the similarity of the numerical values. In the second questionnaire, subjects selected a representative expression for each group, which totaled 11. In the third questionnaire each subject was asked to rank eleven expressions from 1 to 11 with 1 indicating the highest probability. At last, subjects conducted pairwise comparisons to obtain relative weights, which are used to convert into the numerical probability scale.