The purpose of the present invention is to further reliably reduce the contamination of photomask blanks due to the adherence of the dust and particles generated during the storage, transportation, or operation of the container while suppressing the effect on a resist pattern, thereby improving the quality and yield of the photomask blanks. The present invention pertains to a container (1) for storing photomask blanks that stores, transports, or safeguards photomask blanks (2), wherein at least one of the components is constituted by a thermoplastic resin where the amount of caprolactam measured by the dynamic head space method when kept for 60 minutes at 40°C is 0.01 ppm or less n-decane conversion amount per resin weight, and the surface resistance value is no more than 1.0E + 13 ohms.