Abstract: An automatic tool exchanging apparatus of a machine tool comprises a machine body, a tool storage magazine, a spindle attached to the machine body, a tool conveying mechanism and a tool exchanging mechanism which are located between the tool storage magazine and the spindle for exchanging a tool in the magazine with a tool in the spindle, and a drive unit for driving the tool exchanging and tool conveying mechanisms. The tool conveying mechanism comprises a guide bar horizontally arranged between a predetermined position of the tool storage magazine and an intermediate tool pot of the tool exchanging mechanism, a tool carriage movably supported by the guide bar, a tool carriage reciprocating mechanism, a tool conveying arm member rotatably supported by the tool carriage and provided with clamp arms to clamp a tool, a tool conveying arm member rotating mechanism, and a tool conveying arm member reciprocating mechanism.