Obtained is a coating agent that contains a hydroxyalkyl cellulose, which contains more than 50% by mass but 60% by mass or less of a hydroxy alkyl group relative to the total mass of the hydroxyalkyl cellulose, in an amount of from 1% by mass to 7% by mass (inclusive) relative to the total mass of the coating agent. A solid preparation is obtained by spraying this coating agent onto a base tablet and drying this coating agent thereon.
