One solid preparation of the present invention mainly includes silicon fine particles, and has a capability of generating hydrogen. In addition, one specific example of the solid preparation mainly includes silicon fine particles having a crystallite diameter principally of 1 nm or more and 100 nm or less, and exhibits a capability of generating hydrogen in an amount of 3 ml/g or more when brought into contact with a water-containing liquid having a pH value of 7 or more. In this solid preparation, hydrogen is generated when the silicon fine particles are brought into contact with a water-containing liquid having a pH value of 7 or more. Therefore, taking advantage of the characteristics of the solid preparation, generation of hydrogen is promoted in, for example, a gastrointestinal tract where the pH value is 7 or more due to secretion of pancreatic fluid after passage through the stomach after oral ingestion.
