Abstract: A mattress and a laid bedding for a bed are disclosed. The laid bedding is configured such that a mattress in which split cores are freely combined is laid and filled in a box-like closed bottom frame composed of a bottom and an edge erected on a peripheral portion of the bottom. In the mattress, there are three types: a mattress composed of a latex layer, a urethane layer and a low-resilience urethane layer; a mattress composed of an extremely fine fibrous resin layer in which extremely fine fibrous resin is three-dimensionally intertwined and welded together, a urethane layer and a latex layer; and a mattress composed of an extremely fine fibrous resin layer in which extremely fine fibrous resin is three-dimensionally intertwined and welded together, a urethane layer and a low-resilience urethane layer. Each of the mattresses is composed of three or six cores according to size.