A tunnel excavator includes a pair of cutters arranged side by side at a front portion of a tunnel excavator main body. These cutters rotate in opposite directions for excavating the earth to form excavation and for causing the excavated earth to move toward a center area between the pair of cutters. The tunnel excavator further includes a screw cutter extending horizontally in a width direction of the tunnel excavator behind the pair of cutters at a lower level. The screw cutter has a pair of flights spiraling in opposite directions toward the center from opposite ends of the screw cutter for gathering the excavated earth to the center of the screw cutter. A soil plate generally extends along and behind the screw cutter and pushes the excavated earth as the tunnel excavator advances, but the soil plate has an outlet at a lower center area thereof for allowing the excavated earth to pass therethrough. A conveyor is provided behind the soil plate outlet.