A platen for use in thermal printer of a type designed to effect a printing with the use of at least one thermal print head for printing on a recording medium positioned between the platen and the thermal print head, which platen comprises a generally elongated elastic body having an exterior surface adapted to be brought into contact with the heating elements of the thermal print head assembly with at least the recording medium intervening therebetween, and a layer of porous material lined on the exterior surface of the elastic body and having a hardness greater than that of the elastic body and also having a thermal conductivity lower than that of the elastic body. The thermal conductivity and the porosity of the layer of porous material may be within the range of 0.05 to 0.10 Kcal/m.sup.2 .multidot.hr.multidot..degree.C. and within the range of 50 to 95%, respectively.