The objective of this study is to clear the relative semantic properties of to-Infinitive and Gerund and frame a theory that reasonably and comprehensively explains their usages. Before framing a theory, this study selected Bolinger(1968), Jacobson(1982), Wierzbica(1988) and Langacker(1991) as the previous representative researchers, and reviewed the validity of their study results. Bolinger(1968) asserted that “Gerund represents ‘factual things’, ‘realized things’ in the past, and to-Infinitive represents ‘subjunctive or unrealized things’ in the future”. Jacobson(1982) said, “There is a tendency that when mentioning general behaviors, Gerund is used, and when mentioning specific behaviors, to-Infinitive is used. Wierzbica(1988) asserted that “The verb in the main clause, which is combined with to-Infinitive complement, implies ‘want’.” However, considering the results of previous studies for the purpose of promoting the comprehensive validity of semantic studies on to-Infinitive and Gerund, this study organized 6 propositions like below, some times inductively and other times deductively. For this, this study looked into the meanings of preposition ‘to’ in relation with to-Infinitive. We confirmed that this becomes a decisive clue in understanding the meanings and usages of to-Infinitive as well as it has a direct and indirect usefulness in clearing the meanings and usages of Gerund complement.