The invention allows delivery of a substance to be injected to the depth of the intended skin structure in a live body without use of an injection needle. The injector is needle free and is provided with an ignition device with ignition chemical comprising a fuel component and an oxidant component a combustion chamber into which flows the combustion product produced by the reaction of the fuel component with the oxidant component in the combustion of the ignition chemical and in which is accommodated a gas generating agent which is burned by said combustion product to generate a prescribed gas and an enclosing part in which the substance to be injected is enclosed. The injector is configured so that pressure inside the combustion chamber pressurizes the substance to be injected which is enclosed in the enclosing part. The fuel component and oxidant component contained in the ignition chemical are determined so that when mixed in a stoichiometric ratio and burned and the combustion product reaches room temperature gaseous components have been eliminated from said combustion product. A cooling part which is able to contact the combustion product generated by the combustion of the ignition chemical and which cools said combustion product is disposed in the combustion chamber.
