Dead lock is one of the most serious and complex problems concerning the reliability of concurrent Java programs. In this paper, we discuss how to dynamically detect dead locks in concurrent Java programs at run-time, and propose a representation of synchronization waiting state in an execution of a Java program, which is named the Java Thread-Wait-For Graph. We explicitly define all types of dead locks in Java with This representation and present an algorithm to detect the dead locks. Two implementation methods are also presented. We had succeeded in detecting a deadlock from a concurrent program including all types of synchronization waiting relations by our tool.