An image generation device comprising a computer as a control unit that is configured to generate an output image based on a plurality of input images captured by a plurality of cameras (2, 2L, 2R, 2B) attached to an operation target body, wherein the control unit is configured in such a manner that: respective input image portions of two of the plurality of cameras (2, 2L, 2R, 2B) corresponding to an overlap region of respective imaging ranges of two of the plurality of cameras (2, 2L, 2R, 2B) are disposed to form a lattice pattern in the output image, the lattice pattern is generated by using, as a unit pattern, lattice points divided by a circle indicating a mountain of a first wave when the position of a first camera is considered as a simulated wave source, a circle indicating a valley of the first wave, a circle indicating a mountain of a second wave when the position of a second camera is considered as a simulated wave source, and a circle indicating a valley of the second wave, Characterized in that the values of pixels that form the unit pattern are values obtained by weight-averaging values of pixels of a first input image captured by the first camera and values of pixels of a second input image captured by the second camera, in one of a unit pattern through which an abdominal line formed by the first wave and the second wave passes and a unit pattern through which a nodal line formed by the first wave and the second wave passes, a weighted average value of the values of the pixels of the first input image relating to respective pixels is larger than a weighted average value of the values of the pixels of the second input image relating to the respective pixels, and in the other one thereof, a weighted average value of the values of the pixels of the first input image relating to respective pixels is smaller than a weighted average value of the values of the pixels of the second input image relating to the respective pixels, and a weight of a value of each pixel of the first input image and a weight of a value of each pixel of the second input image are determined according to a physical quantity relating to an amplitude of a composite wave of the first wave and the second wave. respective input image portions of two of the plurality of cameras (2, 2L, 2R, 2B) corresponding to an overlap region of respective imaging ranges of two of the plurality of cameras (2, 2L, 2R, 2B) are disposed to form a lattice pattern in the output image, the lattice pattern is generated by using, as a unit pattern, lattice points divided by a circle indicating a mountain of a first wave when the position of a first camera is considered as a simulated wave source, a circle indicating a valley of the first wave, a circle indicating a mountain of a second wave when the position of a second camera is considered as a simulated wave source, and a circle indicating a valley of the second wave, Characterized in that the values of pixels that form the unit pattern are values obtained by weight-averaging values of pixels of a first input image captured by the first camera and values of pixels of a second input image captured by the second camera, in one of a unit pattern through which an abdominal line formed by the first wave and the second wave passes and a unit pattern through which a nodal line formed by the first wave and the second wave passes, a weighted average value of the values of the pixels of the first input image relating to respective pixels is larger than a weighted average value of the values of the pixels of the second input image relating to the respective pixels, and in the other one thereof, a weighted average value of the values of the pixels of the first input image relating to respective pixels is smaller than a weighted average value of the values of the pixels of the second input image relating to the respective pixels, and a weight of a value of each pixel of the first input image and a weight of a value of each pixel of the second input image are determined according to a physical quantity relating to an amplitude of a composite wave of the first wave and the second wave.