Compressed baby milk powder (solid milk) has proven to be very convenient for consumers because it can be easily handled and because a measuring scoop is not needed while using it. Its typical manufacturing process consists of the following steps: (1) moulding of the milk powder by using low compression pressure, (2) humidification of the compressed milk powder on a stainless steel tray, and (3) drying of the humidified compressed milk powder by using a desiccant. This study was conducted to resolve the problem of the sticking of the compressed milk powder to the tray immediately after the humidification-drying process during the manufacture of solid milk. The use of baby milk powder containing α-lactose monohydrate improved the surface structure of solid milk, which reduced stickiness. Thus, the problem of stickiness was solved, while retaining the necessary hardness and rapid solubility of the final product. Studies investigating the mechanism for improving the surface structure of solid milk showed that the presence of α-lactose monohydrate in milk powder influenced the crystallization process starting from an amorphous state.