The present invention relates to an oral solid preparation composition comprising: a proton pump inhibitor or a pharmaceutically acceptable salt thereof; and a binding liquid comprising a basic additive, wherein the content of the basic additive is 2-13 parts by weight relative to 100 parts by weight of the proton pump inhibitor or the pharmaceutically acceptable salt thereof, to an oral solid preparation comprising the same, and to a preparation method therefor. According to the present invention, an oral solid preparation can be provided that has a remarkable reduction in the generation of impurities and excellent stability in moisture and low pH.