The invention discloses a reactor pressure vessel bottom head penetration piece inner wall inspection apparatus. The apparatus comprises a support for fixedly arranging an ultrasound and eddy current combination probe or camera, a second axial driving mechanism for driving the support to move along the axial direction of a penetration piece, a second circumferential driving mechanism for driving the support to move along the circumferential direction of the penetration piece, a second positioning mechanism for realizing positioning of the inner inspection apparatus, and a second buoyancy block arranged at the upper end of the inner wall inspection apparatus. The inner wall inspection apparatus has a compact structure and a small size, can easily and accurately enter the penetration piece under the driving of an operating platform in order to carry out scanning; the apparatus does not generate too large transverse overturning force on the penetration piece due to its small volume weight even if the apparatus shakes; and the buoyancy block offsets the gravity of the inspection apparatus in order to realize stable and easy positioning.