A laser 2-focus velocimeter (L2F) with a micro-scale probe was used for measurements of the velocity and size of droplets in diesel sprays. The diameter of the nozzle orifice was 0.113 mm. The injection pressure was set at 40, 80, and 120 MPa by using a common rail system and the ambient pressure was set at 0.1 to 3.0 MPa. The focusing lens of the L2F was set inside a constant volume vessel, and a measurement position was located at 15 mm from the nozzle exit. It was confirmed that no droplet was observed by the L2F before the spray tip reached the measurement position in a high ambient pressure condition. The effect of the ambient pressure on the droplet velocity was found to be small in the near nozzle region. The droplet size decreased when the ambient pressure increased from 0.1 to 1.0 MPa. The droplet size increased when the ambient pressure equal to or increased higher than 2.0 MPa. These tendencies were verified by the KIVA-3V simulation.