Disclosed are an illumination device capable of improving an optical efficiency of a light generated from a light source and a reflection type liquid crystal device using the, illumination device. Between at least one light source and a first light guiding plate, which is provided to uniformly project the light incident from a first side towards a second side, a second light guiding plate for projecting the incident light towards the first side of the first light guiding plate is provided. A distance between a light projecting portion of the second light guiding plate and a light reflecting portion opposite the light projecting portion becomes narrow as an amount of light flux of the light emitted from at least one light source decreases. Accordingly, the light efficiency can be improved by increasing the probability of variation in optical routes for the light generated from each light source, though the number of the light sources disposed at a side of the second light guiding plate is increased.