As a new heat exchanger with a high heat transfer density, a perforated fin heat exchanger effectively utilizing intense turbulence is proposed. The principal modification from the conventional perforated fin heat exchanger is the flow direction, which is normal or oblique to the perforated fins; that is, the working fluid is forced to flow irregularly through fin holes, which generates an intense turbulence field. For the six test cores using three types of perforated fin, friction loss and heat transfer experiments are conducted. The overall heat transfer coefficient of each test core is measured by the modified single-blow method. The heat transfer coefficients per unit volume of the present heat exchanger are found to be very high. The heat transfer performance is discussed taking the pumping power into account.