A light source apparatus outputs light for an endoscope apparatus. A blue LED emits blue light with a peak wavelength equal to or longer than 450 nm. A wavelength cut-off filter is disposed downstream of the blue LED, for cutting off a component in the blue light having a wavelength equal to or longer than the peak wavelength. Preferably, the wavelength cut-off filter cuts off a component of a wavelength equal to or longer than a reference wavelength in a wavelength range equal to or longer than the peak wavelength. A mode changer changes over an enhancement mode and a normal mode, the enhancement mode is set for enhancing and imaging a surface blood vessel of the object by use of the wavelength cut-off filter, the normal mode is set for imaging the object by disabling a function of the wavelength cut-off filter.
