A slim type lamp apparatus of a vehicle may include a light source for radiating light; and a lens portion including an incident portion through which the light radiated by the light source is incident, a reflection portion extending from the incident portion to reflect and move the incident light, and an emission portion extending from the reflection portion and emitting the light reflected by the reflection portion, the reflection portion diffusing some light upon reflection of the light to form a diffusion beam pattern by the emission portion and condensing other light upon reflection to form a condensing beam pattern by the emission portion.