To provide a capsule for a planter for protecting plants inside a cultivation container from the harm of winds, rain and frost.

This capsule is a transparent capsule 1 to be put on the planter 2 for cultivating the plants and the capsule 1 is freely detachably mounted along the upper end outer peripheral edge of the planter 2 and is provided with many air holes. The air holes are composed of a large air take-in hole 4 provided near the lower end part of the capsule and plural small holes 5 formed with appropriate intervals on the capsule 1 and a locking means to be locked to the upper end outer peripheral edge 3 of the planter is provided on the lower end part of the capsule.