It is intended to provide resin foamed particles having a high environmental compatibility. Furthermore, it is intended to provide an economical and easy-to-use method of producing resin foamed particles having biodegradability without using a crosslinking agent, which should be handled with care, in the step of producing foamed resin particles. It is also intended to provide a molded article made of foamed particles having an extremely high heat insulating property and a biodegradability. Thermoplastic polyester-type resin foamed particles, in which the ratio of cells with diameter of 50 μm or less amounts to 20% or more in an arbitrary two-dimensional section of a thermoplastic polyester-type resin foamed particles, are first produced and then a molded article is produced with the use of these resin foamed particles.