The present invention relates to a portable digital reader for reading an analysis target chip including a plurality of test areas. The reader comprises: a light emitting section having light emitting elements for radiating light; an integral optical splitter for uniformly distributing the light from the light emitting section to each test area of the analysis target chip; a light receiving section for receiving light reflected from each test area so as to convert the same into electric signals; and a measuring section for measuring concentration according to the electric signals obtained from the light receiving section. Therefore, it is possible to prevent the generation of errors in signal measurement due to optical distribution failure by assembling branch sections of the optical splitter under the control of the number of the branch sections according to the number of test items in a test strip.