An endoscope having an imaging unit at a tip portion of an insertion unit to be inserted into a body cavity, the imaging unit comprising: a solid-state imaging device which is disposed in such a manner that a photodetecting surface thereof crosses a longitudinal direction of the insertion unit and which performs photoelectric conversion on an optical image formed on the photodetecting surface; a circuit board having a connection surface facing the back surface of the solid-state imaging device, which back surface is opposite to the photodetecting surface and formed with connection terminals, and which connection surface serves for electrical connection to the connection terminals of the solid-state imaging device, wherein the circuit board is a rigid board that is L-shaped when viewed in a width direction of the circuit board that is perpendicular to the longitudinal direction of the insertion unit; of a first leg and a second leg that constitute the L-shaped circuit board and are perpendicular to each other, the first leg which is opposed to the solid-state imaging device has the connection surface on the side of the solid-state imaging device and transmission cables are electrically connected to an inner surface of the second leg, the inner surface having a smaller area, than an area of an outer surface of the second leg, in a plane including the longitudinal direction of the insertion unit and the width direction of the circuit board, the outer surface being opposite to the inner surface, characterized in that: the transmission cables have four or more cables including a first cable having a first diameter and a second cable having a second diameter, the first diameter being larger relative to the smaller second diameter; the four or more cables are arranged on the inner surface of the second leg of the circuit board in the width direction of the circuit board; and the first cable is located at an outermost position in the width direction of the circuit board. a solid-state imaging device which is disposed in such a manner that a photodetecting surface thereof crosses a longitudinal direction of the insertion unit and which performs photoelectric conversion on an optical image formed on the photodetecting surface; a circuit board having a connection surface facing the back surface of the solid-state imaging device, which back surface is opposite to the photodetecting surface and formed with connection terminals, and which connection surface serves for electrical connection to the connection terminals of the solid-state imaging device, wherein the circuit board is a rigid board that is L-shaped when viewed in a width direction of the circuit board that is perpendicular to the longitudinal direction of the insertion unit; of a first leg and a second leg that constitute the L-shaped circuit board and are perpendicular to each other, the first leg which is opposed to the solid-state imaging device has the connection surface on the side of the solid-state imaging device and transmission cables are electrically connected to an inner surface of the second leg, the inner surface having a smaller area, than an area of an outer surface of the second leg, in a plane including the longitudinal direction of the insertion unit and the width direction of the circuit board, the outer surface being opposite to the inner surface, characterized in that: the transmission cables have four or more cables including a first cable having a first diameter and a second cable having a second diameter, the first diameter being larger relative to the smaller second diameter; the four or more cables are arranged on the inner surface of the second leg of the circuit board in the width direction of the circuit board; and the first cable is located at an outermost position in the width direction of the circuit board. the transmission cables have four or more cables including a first cable having a first diameter and a second cable having a second diameter, the first diameter being larger relative to the smaller second diameter; the four or more cables are arranged on the inner surface of the second leg of the circuit board in the width direction of the circuit board; and the first cable is located at an outermost position in the width direction of the circuit board.