This paper presents the design of a compact size projectile accelerator, and its application. To meet the various needs such as a compact body size to use under various experimental conditions, an easy maintenance for repetitive experiments during a certain period, and a capability of the velocity control, the compact accelerators were newly designed with a direct explosive drive method. Two different types of accelerator were designed: a PMMA accelerator and a metal accelerator. The pictures of the projectile shoot using the designed accelerators were recorded by SHIMADZU HyperVision HPV-1 high-speed video camera. As a result, it was recognized that the PMMA accelerator was failed to accelerate the projectile, while the metal accelerator succeeded to accelerate it effectively. The accelerating performance of the metal accelerator was further investigated. The explosives for projectile acceleration were Emulsion explosive and Composition C4 explosive weighing 5 to 35g. It was found that the metal accelerator has the capability to control the projectile velocity adjusting the weight of the explosives, and there is an approximate linear correlation between them in our experimental range. A series of impact tests on 5052S aluminum alloy targets was examined using the accelerator.