A cooling device comprising: a shell having a shell main body formed in a cylindrical shape extending around an axis, an inlet nozzle configured to feed a fluid into the shell main body, and an outlet nozzle disposed away from the inlet nozzle in an axial direction in which the axis extends and configured to feed the fluid inside the shell main body to an outside of the shell main body; a cooler disposed inside the shell main body, configured to cool the fluid flowing from the inlet nozzle toward the outlet nozzle by internally circulating the fluid, and having a first surface extending in the axial direction to face the inlet nozzle and the outlet nozzle; and a partition member fixed to the first surface, and partitioning a space portion between the cooler and an inner peripheral surface of the shell main body into a first space communicating with the inlet nozzle and a second space communicating with the outlet nozzle, wherein the partition member includes a main partition plate disposed between the inlet nozzle and the outlet nozzle in the axial direction, and extending from the first surface to the inner peripheral surface of the shell main body to spread in a direction intersecting with the axis, a first guide portion extending from an end portion on a first side of the main partition plate in the direction intersecting with the axis toward a first end surface of the shell main body close to the inlet nozzle in the axial direction, and a second guide portion extending from an end portion on a second side of the main partition plate in the direction intersecting with the axis toward a second end surface of the shell main body close to the outlet nozzle in the axial direction, characterized in that the main partition plate spreads to be inclined with respect to a plane orthogonal to the axial direction. a shell having a shell main body formed in a cylindrical shape extending around an axis, an inlet nozzle configured to feed a fluid into the shell main body, and an outlet nozzle disposed away from the inlet nozzle in an axial direction in which the axis extends and configured to feed the fluid inside the shell main body to an outside of the shell main body; a cooler disposed inside the shell main body, configured to cool the fluid flowing from the inlet nozzle toward the outlet nozzle by internally circulating the fluid, and having a first surface extending in the axial direction to face the inlet nozzle and the outlet nozzle; and a partition member fixed to the first surface, and partitioning a space portion between the cooler and an inner peripheral surface of the shell main body into a first space communicating with the inlet nozzle and a second space communicating with the outlet nozzle, wherein the partition member includes a main partition plate disposed between the inlet nozzle and the outlet nozzle in the axial direction, and extending from the first surface to the inner peripheral surface of the shell main body to spread in a direction intersecting with the axis, a first guide portion extending from an end portion on a first side of the main partition plate in the direction intersecting with the axis toward a first end surface of the shell main body close to the inlet nozzle in the axial direction, and a second guide portion extending from an end portion on a second side of the main partition plate in the direction intersecting with the axis toward a second end surface of the shell main body close to the outlet nozzle in the axial direction, a main partition plate disposed between the inlet nozzle and the outlet nozzle in the axial direction, and extending from the first surface to the inner peripheral surface of the shell main body to spread in a direction intersecting with the axis, a first guide portion extending from an end portion on a first side of the main partition plate in the direction intersecting with the axis toward a first end surface of the shell main body close to the inlet nozzle in the axial direction, and a second guide portion extending from an end portion on a second side of the main partition plate in the direction intersecting with the axis toward a second end surface of the shell main body close to the outlet nozzle in the axial direction, characterized in that the main partition plate spreads to be inclined with respect to a plane orthogonal to the axial direction.