Polythiol compound for optical material and preparation method therefor, and method for preparing polyol compound

A polythiol compound of an embodiment, which is obtained by reacting a sulfide compound having two or more triple bonds with an alcohol compound having a mercapto group to prepare a tetrafunctional or higher functional polyol compound containing sulfur, followed by reaction with thiourea and hydrolysis, can provide, through reaction with an isocyanate compound, a polythiourethane-based compound having excellent optical characteristics, such as a refractive index and an Abbe number, and excellent heat resistance and impact resistance, and thus, is useful for the preparation of optical materials, such as spectacle lenses and camera lenses. According to the preparation method of another embodiment, a colorless transparent polyol having improved yield and purity while shortening the reaction time can be prepared, and a clear optical lens having low yellowness can be prepared using the polyol.