5 5 or more the linear expansion coefficient of the foamed sheet tends to decrease with the increase of ratio l max l min and the upper limit of the ratio is not particularly limited however usually when the value of the ratio exceeds about 7 the effect of reducing a linear expansion coefficient becomes almost constant thus the above ratio is usually set at 7 or less the foamed sheets of the present invention having such a feature have a low linear expansion coefficients and therefore can be suitably used for applications where foamed sheets are required to show small dimensional changes with temperature changes the foamed sheet of the present invention is made of a thermoplastic resin material and the thermoplastic resin material comprises at least one kind of thermoplastic resin the kind of the thermoplastic resin which constitutes the thermoplastic resin material is not particularly limited as long as it can form foams for example polyolefin resins such as high medium or low density polyethylene and polypropylene polystyrene resin acrylic resin such as poly methyl methacrylate polyamide resin polyester resin and poly vinyl chloride resin may be employed non crosslinked thermoplastic resins are preferable since they can be easily recycled the thermoplastic resins may be either homopolymers or copolymers when two or more kinds of thermoplastic resins are used the mixing proportion of the resins is not particularly limited moreover copolymers are not limited in their monomer compositions the foamed sheet of the present invention may contain additives such as antioxidants ultraviolet absorbers antistatic.