Disclosed is a tunnel excavating apparatus for excavating tunnels in earth. This tunnel excavating apparatus comprises shell bodies, an excavating mechanism disposed on front of the excavating portion shell body, and a propelling mechanism disposed within the shell body. The shell bodies include an excavating portion shell body, a front shell body, and a rear shell body disposed in order from the leading end side in the advancing direction of excavation. The propelling mechanism comprises a projection mechanism and an extension mechanism. The projection mechanism includes front circumferential jacks in the front shell body and rear circumferential jacks in the rear shell body, both of which are capable of extension and contraction in the outer circumferential direction. The extension mechanism includes front axial jacks interposed between the excavating portion shell body and the front shell body, and rear axial jacks interposed between the front shell body and the rear shell body, both of which are capable of extension and contraction in the direction of advancing excavation.