New experimental apparatus was developed for getting extremely high shock pressure. The apparatus utilized convergent collision of metal jets generated between a conical concave metal block and metal flyer plate. That is, since the plate is accelerated toward the metal block by detonation of plastic explosive, metal jets with high velocity are launched from points where the flyer plate collided with the metal block. As the collision points are on a concentric circle of surface of the conical concave metal block, metal jets are launched toward center portion, resulting in the converging collision of the metal jets. From relation among flying velocity of the plate, travelling velocity of the collision point, and deformative inclined angle of the flyer plate in accordance with the detonation of explosive, some of calculated results were derived for estimation for generation limit of the jetting. If launching velocity of the metal jets attains at an order of 10000 m s-1, a head - on collision of the jets will generate relative velocity of about 20000 m s-1. Therefore, the high velocity collision may lead to generation of extremely high shock pressure, for example, an order of TPa.