Abstract: A lid body 200 is divided, on its front side, into three parts, that is, a pair of first movable parts 220 in the form of curved plates on both sides of the body and a second movable part 230 in the form of a flat plate in the middle of the body. A container body 100 is provided with a front engagement member 131 which is displaceable in front and in the rear of the body 100. The first movable parts 220 have front engagement members 221 formed at their front ends to be engageable with the front engagement member 131. While, the second movable part 230 has a disengagement member 231 formed at the front ends. The first movable parts 220 on elastic deformation are engaged with the front engagement member 131. When the second movable part 230 is subjected to depression of its upper face at the front end so that the disengagement member 231 causes the front engagement member 131 to be displaced forward, the engagement of the front engagement member 131 with the front engagement members 221 is released.