The present invention relates to a mattress cushion, wherein it consists of a cushion mattress not using metal components like coil springs, the mattress body (1) is composed of overlapping elastic surface layers (6) (7) on both sides of a core portion (3) consisting of synthetic resin moldings sandwiched therebetween. Accordingly, the mattress cushion is light and there is no problem of rusting. Also, the core portion (3) is composed of alternately upper and lower horizontal walls (22), (23) connected by adjoining vertical side walls (21) (21), and protrusions (27) are formed on each vertical side wall (21). Accordingly, the mattress cushion increases in strength and improves the ventilation and comfort of the user.