To provide a mattress for a bed in which problems on a conventional mattress for a bed are solved and which is remarkably improved on weight reduction and has excellent air permeability, dehumidifying properties, moisture releasing properties, heat retaining properties, mildew resistance, light-weight and durability.

The mattress for the bed characterized by having at least one sheet of a three-dimensional knit with a fiber filling ratio of at most 20% and a thickness of 5-60 mm in which top and bottom ground textures are connected with a connecting thread as a middle padding material and the total thickness of the three-dimensional knit being at least 45% of the thickness of the whole mattress is provided.