To provide an expansion type partition which can cope with an amount of content corresponding to at least an expanded space even when a travel case is used in such an expanded size that a space between the lid-side shell and body-side shell of the travel case is expanded and which enables an internal engagement device to be easily engaged with a case-side receiving device.

A gusset 4 is provided between a base edge 2 and a leading edge 3 in a partition 1. In addition, an open fastener 7 is provided which can disengage a first side 5 of a base edge 2 of the gusset 4 and a second side 6 of the leading edge 3 thereof. By disengaging the first side 5 and second side 6 engaged by the open fastener 7, the partition 1 can be extended by a length corresponding to at least the width of the gusset in the direction of the leading edge 3.