A quick coupler, the quick coupler comprising: a quick coupler body connectable to an arm of an excavator; a fixing hook provided at a first side of the quick coupler body, engageable with a first attachment pin, and provided with a stopping protrusion having an opening-side end portion protruding upwardly; a hitch provided at a second side of the quick coupler body, and connected to a cylinder rod of a main-cylinder to be engaged with a second attachment pin when the cylinder rod performs forward operation; and a first locking means for preventing locking engagement between the fixing hook and the first attachment pin from being arbitrarily released, wherein the first locking means comprises: a first support plate fixed to the quick coupler body; a sub-cylinder mounted to the first support plate and in which a sub-rod is retracted; a moving plate having a first support step that is connected to the sub-rod and a safety plate at a lower surface of the moving plate, and disposed to be moveable in a sliding manner toward an upper side of the fixing hook; and at least one DIE-spring fixed to the first support plate by a support means, and transmitting an elastic force to allow the moving plate to be positioned at the upper side of the fixing hook characterized in that the support means comprises: a support bolt passing through the DIE-spring to be locked to the first support plate and to support a first end of the DIE-spring; and a locking step protruding from an upper surface of the moving plate, coupled to the support bolt that passes therethrough, and supporting a second end of the DIE-spring. a quick coupler body connectable to an arm of an excavator; a fixing hook provided at a first side of the quick coupler body, engageable with a first attachment pin, and provided with a stopping protrusion having an opening-side end portion protruding upwardly; a hitch provided at a second side of the quick coupler body, and connected to a cylinder rod of a main-cylinder to be engaged with a second attachment pin when the cylinder rod performs forward operation; and a first locking means for preventing locking engagement between the fixing hook and the first attachment pin from being arbitrarily released, wherein the first locking means comprises: a first support plate fixed to the quick coupler body; a sub-cylinder mounted to the first support plate and in which a sub-rod is retracted; a moving plate having a first support step that is connected to the sub-rod and a safety plate at a lower surface of the moving plate, and disposed to be moveable in a sliding manner toward an upper side of the fixing hook; and at least one DIE-spring fixed to the first support plate by a support means, and transmitting an elastic force to allow the moving plate to be positioned at the upper side of the fixing hook characterized in that the support means comprises: a support bolt passing through the DIE-spring to be locked to the first support plate and to support a first end of the DIE-spring; and a locking step protruding from an upper surface of the moving plate, coupled to the support bolt that passes therethrough, and supporting a second end of the DIE-spring. a first support plate fixed to the quick coupler body; a sub-cylinder mounted to the first support plate and in which a sub-rod is retracted; a moving plate having a first support step that is connected to the sub-rod and a safety plate at a lower surface of the moving plate, and disposed to be moveable in a sliding manner toward an upper side of the fixing hook; and at least one DIE-spring fixed to the first support plate by a support means, and transmitting an elastic force to allow the moving plate to be positioned at the upper side of the fixing hook characterized in that the support means comprises: a support bolt passing through the DIE-spring to be locked to the first support plate and to support a first end of the DIE-spring; and a locking step protruding from an upper surface of the moving plate, coupled to the support bolt that passes therethrough, and supporting a second end of the DIE-spring. a support bolt passing through the DIE-spring to be locked to the first support plate and to support a first end of the DIE-spring; and a locking step protruding from an upper surface of the moving plate, coupled to the support bolt that passes therethrough, and supporting a second end of the DIE-spring.