An endoscope apparatus comprising: an active grasping forceps as an active accessory including, at a distal end thereof, a grasping portion as an actuation portion, which is configured to be actuated to be opened or closed, and a forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) configured to be actuated to make the grasping forceps perform an active movement; an operating means for operating the grasping portion to be opened or closed; an endoscope including a first accessory insertion pass wherein the grasping forceps is adapted to be inserted through the first accessory insertion pass from a proximal end portion of the first accessory insertion pass to a distal end portion of the first accessory insertion pass, and projected from and retracted into the distal end portion of the first accessory insertion pass, and a detecting means, a forceps roller provided on the proximal end portion of the first accessory insertion pass, configured to be rotated according to a forward and backward movement of the grasping forceps and including a forceps encoder configured to output rotation angle data to the detecting means; characterized by the detecting means being further configured to store data of a length from the distal end portion of the first accessory insertion pass to the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) and data of the total length of the first accessory insertion pass, calculate data of an insertion amount of the grasping forceps on the basis of the input rotation angle data, detect whether the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is projected from the distal end portion of the first accessory insertion pass or not based on the calculated insertion amount data, storage length data, and storage total length data; and to output the detection data to control means, and if it is detected that the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is not projected from the distal end portion of the first accessory insertion pass, the control means is configured to change to a stopping mode in which the grasping portion is kept in a closing state and the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is kept in a releasing state regardless of an operation of the operating means while, if it is detected that the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is projected from the distal end portion of the first accessory insertion pass, the control means is configured to change to an actuating mode in which the grasping portion is actuated to be opened and closed according to an operation of the operating means, and the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is actuated to be rotated according to an operation of the operating means. an active grasping forceps as an active accessory including, at a distal end thereof, a grasping portion as an actuation portion, which is configured to be actuated to be opened or closed, and a forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) configured to be actuated to make the grasping forceps perform an active movement; an operating means for operating the grasping portion to be opened or closed; an endoscope including a first accessory insertion pass wherein the grasping forceps is adapted to be inserted through the first accessory insertion pass from a proximal end portion of the first accessory insertion pass to a distal end portion of the first accessory insertion pass, and projected from and retracted into the distal end portion of the first accessory insertion pass, and a detecting means, a forceps roller provided on the proximal end portion of the first accessory insertion pass, configured to be rotated according to a forward and backward movement of the grasping forceps and including a forceps encoder configured to output rotation angle data to the detecting means; characterized by the detecting means being further configured to store data of a length from the distal end portion of the first accessory insertion pass to the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) and data of the total length of the first accessory insertion pass, calculate data of an insertion amount of the grasping forceps on the basis of the input rotation angle data, detect whether the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is projected from the distal end portion of the first accessory insertion pass or not based on the calculated insertion amount data, storage length data, and storage total length data; and to output the detection data to control means, and if it is detected that the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is not projected from the distal end portion of the first accessory insertion pass, the control means is configured to change to a stopping mode in which the grasping portion is kept in a closing state and the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is kept in a releasing state regardless of an operation of the operating means while, if it is detected that the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is projected from the distal end portion of the first accessory insertion pass, the control means is configured to change to an actuating mode in which the grasping portion is actuated to be opened and closed according to an operation of the operating means, and the forceps joint portion (88 1, 88 2, 88 3, 88 4, 88 5) is actuated to be rotated according to an operation of the operating means.