A scramjet engine comprising: a first flow path forming member (1;2); a second flow path forming member (2;1) provided in opposite to the first flow path forming member (1;2); a first fuel injection device; and a second fuel injection device, wherein a flow path is formed between the first flow path forming member (1;2) and the second flow path forming member (2;1), wherein the flow path includes: a turbulence formation region where a compressed air is introduced from upstream; a combustion region that is located downstream of the turbulence formation region and where a combustion using the compressed air is carried out, and an upstream region configured to introduce the compressed air to the turbulence forming region, wherein the second flow path forming member (2;1) is formed with a protrusion located in the turbulence formation region and protruding toward the first flow path forming member (1;2), wherein the first fuel injection device is configured to inject fuel into the compressed air via a first fuel nozzle provided to the protrusion, wherein the second flow path forming member (2;1) is formed with a cavity located in the combustion region, wherein the second fuel injection device is configured to inject fuel into the compressed air via a second fuel nozzle provided to the cavity, wherein the cavity comprises: a bottom surface; and an inclined surface connected to a downstream side end of the bottom surface, and wherein an inclination of the inclined surface of the cavity is adjustable so that a shock wave is generated in operation in the combustion region, the shock wave generating a discontinuity surface which reaches inside the cavity, wherein the second fuel nozzle is formed at the inclined surface of the cavity such that the second fuel injection device can inject fuel from a location downstream of the discontinuity surface to a location upstream of the discontinuity surface so that the fuel crosses the discontinuity surface, and wherein an angle (θ 1) between the inclined surface of the cavity and a first surface that is a surface of a part of the second flow path forming member (2;1) that faces the upstream region is less than or equal to 45 degrees. a first flow path forming member (1;2); a second flow path forming member (2;1) provided in opposite to the first flow path forming member (1;2); a first fuel injection device; and a second fuel injection device, wherein a flow path is formed between the first flow path forming member (1;2) and the second flow path forming member (2;1), wherein the flow path includes: a turbulence formation region where a compressed air is introduced from upstream; a combustion region that is located downstream of the turbulence formation region and where a combustion using the compressed air is carried out, and an upstream region configured to introduce the compressed air to the turbulence forming region, a turbulence formation region where a compressed air is introduced from upstream; a combustion region that is located downstream of the turbulence formation region and where a combustion using the compressed air is carried out, and an upstream region configured to introduce the compressed air to the turbulence forming region, wherein the second flow path forming member (2;1) is formed with a protrusion located in the turbulence formation region and protruding toward the first flow path forming member (1;2), wherein the first fuel injection device is configured to inject fuel into the compressed air via a first fuel nozzle provided to the protrusion, wherein the second flow path forming member (2;1) is formed with a cavity located in the combustion region, wherein the second fuel injection device is configured to inject fuel into the compressed air via a second fuel nozzle provided to the cavity, wherein the cavity comprises: a bottom surface; and an inclined surface connected to a downstream side end of the bottom surface, and a bottom surface; and an inclined surface connected to a downstream side end of the bottom surface, and wherein an inclination of the inclined surface of the cavity is adjustable so that a shock wave is generated in operation in the combustion region, the shock wave generating a discontinuity surface which reaches inside the cavity, wherein the second fuel nozzle is formed at the inclined surface of the cavity such that the second fuel injection device can inject fuel from a location downstream of the discontinuity surface to a location upstream of the discontinuity surface so that the fuel crosses the discontinuity surface, and wherein an angle (θ 1) between the inclined surface of the cavity and a first surface that is a surface of a part of the second flow path forming member (2;1) that faces the upstream region is less than or equal to 45 degrees.