A coating agent containing a hydroxyalkyl cellulose in an amount of 1% by mass or more and 7% by mass or less, based on the total amount of the coating agent, the hydroxyalkyl cellulose having hydroalkyl groups in an amount of more than 50% by mass and 60% by mass or less, based on the total amount of the hydroxyalkyl cellulose is obtained. A solid preparation is obtained by spraying the coating agent to a plane tablet and then drying.本發明獲得一種被覆劑，其相對於被覆劑之總質量，含有1質量%以上且7質量%以下之羥烷基纖維素，該羥烷基纖維素之羥烷基的含量相對於羥烷基纖維素之總質量超過50質量%且在60質量%以下。將該被覆劑霧狀噴至素錠並進行乾燥而獲得固形製劑。
