An experimental study on the improvement of aerodynamic characteristics of space transportation system by lateral blowing in subsonic flow has been conducted. The model configuration is winged body which has 75°/45° double delta wing of modified NACA0010. Lateral blowing is realized by injecting a pair of sonic jets parallel to the trailing edge of the wing. The experiments have been conducted in the transonic wind tunnel of ISAS (Institute of Space and Astronautical Science), JAXA (Japan Aerospace Exploration Agency), Japan under the test condition of free-stream Mach number M∞ =0.3, Reynolds number Re =2.14 × 106, angle of attack α= -15 °~40 °, jet momentum coefficient Cμ=0.0166, 0.0295 and 0.0398. The results show that lateral blowing increases the lift and lift-to-drag ratio over the wide range of angle of attack. Larger enhancement of the lift is obtained especially above 15 °. Larger increase of the lift-to-drag ratio is obtained especially below 10 °. From these results, we confirmed that lateral blowing can be useful for the improvement of aerodynamic characteristics of the space transportation system in subsonic flow.