An injector can include an ignition device having a partition member which forms a first space to store a gunpowder and which is formed of a prescribed rigid material such that the partition member is breached based on a rise in pressure of the first space when the gunpowder is burned. The injector can also include a case including a base section fixed on a side of the ignition device. The case can be arranged in a space inside the injector main body so as to cover the ignition device. The case can define a second space with the partition member of the ignition device and encapsulate, inside the second space, a combustion product of the gunpowder. When the gunpowder burns in the ignition device and pressure inside the second space rises, a part of the case extends so as to approach a prescribed end section.