A measuring apparatus , comprising: a support plate comprising an upper surface on a central portion of which an object is to be mounted, the support plate being rotatable about an axis of rotation extending vertically from the central portion; an optical sensor disposed above the support plate ; wherein the optical sensor comprises one substrate , a light-emitting element configured to irradiate the object with light, a first light-receiving element configured to receive specular light reflected from the object , and a second light-receiving element configured to receive diffuse light reflected from the object ; and wherein the light-emitting element , the first light-receiving element , and the second light-receiving element are formed on the one substrate in a single-piece construction; a support member which extends vertically and serves as a support; and a securing member which extends from the support member in a direction parallel to the plane of the support plate and which secures the optical sensor ; wherein one end of the securing member is fixed to the support member , and, the other end of the securing member is located in a region above the support plate ; wherein the optical sensor is attached to the securing member so as to be opposed to the support plate , with the securing member lying in between the optical sensor and the support plate ; wherein the other end of the securing member has an opening, whereby the optical sensor is able to irradiate the object with light and receive reflected light through the opening of the securing member ; and wherein the securing member is rotatable about its longitudinal axis. a support plate comprising an upper surface on a central portion of which an object is to be mounted, the support plate being rotatable about an axis of rotation extending vertically from the central portion; an optical sensor disposed above the support plate ; wherein the optical sensor comprises one substrate , a light-emitting element configured to irradiate the object with light, a first light-receiving element configured to receive specular light reflected from the object , and a second light-receiving element configured to receive diffuse light reflected from the object ; and wherein the light-emitting element , the first light-receiving element , and the second light-receiving element are formed on the one substrate in a single-piece construction; a support member which extends vertically and serves as a support; and a securing member which extends from the support member in a direction parallel to the plane of the support plate and which secures the optical sensor ; wherein one end of the securing member is fixed to the support member , and, the other end of the securing member is located in a region above the support plate ; wherein the optical sensor is attached to the securing member so as to be opposed to the support plate , with the securing member lying in between the optical sensor and the support plate ; wherein the other end of the securing member has an opening, whereby the optical sensor is able to irradiate the object with light and receive reflected light through the opening of the securing member ; and wherein the securing member is rotatable about its longitudinal axis. <EOS>