A stretchable flexible substrate according to one aspect of the present disclosure includes: an electronic component; a first insulating layer located around the electronic component and having first and second main surfaces facing each other; a first metal layer that is in contact with the first main surface; a second metal layer that is in contact with the second main surface and electrically connected to the electronic component; and a second insulating layer that seals the electronic component, first insulating layer, and second metal layer, in plan view, a curved wiring portion extending from a central portion made up of at least the electronic component, portions of the first insulating layer and first and second metal layers, the curved wiring portion being made up of at least other portions of the first insulating layer, first and second metal layers, and the curved wiring portion being curved at least partially.