The present invention provides a porous sustained-release body in which transparency of a porous carrier changes. The porous sustained-release body includes an inorganic monolithic porous body 1 including a skeleton body 2 of an inorganic compound and air gaps 3,4 having a three-dimensional continuous network structure formed in the skeleton body 2, and a sustained-release liquid absorbed into air gaps 2, 3, wherein the inorganic monolithic porous body 1 is opaque at an initial state, which is a state before absorption of the sustained-release liquid in which air exists in the air gaps, and refractive index of the sustained-release liquid and refractive index of the skeleton body are the same within an error range within which a portion in which the sustained-release liquid is absorbed into the air gaps changes to transparent or semitransparent.
