PURPOSE: To prevent deterioration of strength in heat-sealing between the upper side of a flange part and the underside of a heatsealing layer, and to prevent a cup-like container from being unsealed with a cover member separated by a method wherein a plurality of looped grooves, each in the depth in specified proportion to the thickness of the heat-sealing layer, are provided to the upper side of the flange part.

CONSTITUTION: One or more looped grooves 11, each in the depth approximately a half of the thickness of a heat-sealing layer 31, are provided to the upper side of a flange part 21 of a cup-like container 20. Thereby, deterioration of strength in heat-sealing does not occur between the upper side of the flange part 21 and the heat-sealing layer 31 as the heat-sealing layer 31 remains approximately at a half of its thickness in the middle of the grooves 11 in one or more numbers when the heat-sealing layer 31 is pushed out toward the right and the left during the process of filling the container with contents and hermetically sealing the container by heat-sealing. Furthermore, the cup-like container 20 can be prevented from being unsealed with its cover member separated when shocks are applied on handling during distribution and sales.