An endoscope apparatus comprising: a longitudinal member that has a longitudinal axis; a subject operation section which is configured to operate a subject, which is provided at a distal end side of the longitudinal member and which is formed by a curved portion that is capable of being curved; a tool channel through which a treatment instrument having an operation section is capable of being inserted along the longitudinal axis; a first transmission portion being connected with the curved portion; a first input portion being connected with the first transmission portion and being capable of driving the first transmission portion so as to curve the curved portion; and a second input portion being connected with the first input portion, an operation section which is different from the operation section of the treatment instrument, which is provided at a proximal end side of the longitudinal member and which has a hole communicating with the tool channel and through which the treatment instrument is insertable, wherein an operation mechanism of the operation section includes the first input portion and the second input portion, and wherein the operation section is adapted to be supported by an operator; and a second transmission portion which is connected with the second input portion; wherein the second input portion is capable of being connected with the operation section of the treatment instrument, the treatment instrument is capable of being inserted into the tool channel via the hole rotatably around the longitudinal axis and slidably along the longitudinal axis, characterized in that the second transmission portion is also connected with the first input portion; the second input portion is capable of being tilt operated toward a predetermined direction by a tilting operation of the treatment instrument, the second input portion is capable of providing a driving force to the second transmission portion by the tilting operation of the operation section of the treatment instrument, and the second transmission portion is capable of transmitting the driving force from the second input portion to the first input portion so as to drive the first input portion for curving the curved portion. a longitudinal member that has a longitudinal axis; a subject operation section which is configured to operate a subject, which is provided at a distal end side of the longitudinal member and which is formed by a curved portion that is capable of being curved; a tool channel through which a treatment instrument having an operation section is capable of being inserted along the longitudinal axis; a first transmission portion being connected with the curved portion; a first input portion being connected with the first transmission portion and being capable of driving the first transmission portion so as to curve the curved portion; and a second input portion being connected with the first input portion, an operation section which is different from the operation section of the treatment instrument, which is provided at a proximal end side of the longitudinal member and which has a hole communicating with the tool channel and through which the treatment instrument is insertable, wherein an operation mechanism of the operation section includes the first input portion and the second input portion, and wherein the operation section is adapted to be supported by an operator; and a second transmission portion which is connected with the second input portion; wherein the second input portion is capable of being connected with the operation section of the treatment instrument, the treatment instrument is capable of being inserted into the tool channel via the hole rotatably around the longitudinal axis and slidably along the longitudinal axis, the second input portion is capable of providing a driving force to the second transmission portion by the tilting operation of the operation section of the treatment instrument, and the second transmission portion is capable of transmitting the driving force from the second input portion to the first input portion so as to drive the first input portion for curving the curved portion.