An optical measurement apparatus includes a spectroscopic measurement device, a first optical fiber for propagating light to be measured, a hemispherical portion having a light diffuse reflection layer on an inner wall of the hemispherical portion, and a plane portion disposed to close an opening of the hemispherical portion and having a mirror reflection layer located to face the inner wall of the hemispherical portion. The plane portion includes a first window for directing the light emitted thorough the first optical fiber into an integrating space. The integrating space is formed by the hemispherical portion and the plane portion. The optical measurement apparatus further includes a second optical fiber for propagating the light in the integrating space to the spectroscopic measurement device through a second window of the plane portion.