Iron oxide nanotubes (NTs) and zinc doped iron oxide NTs were prepared by sol-gel method. Obtained NTs have spinel structure represented by ZnδFe3-δO4. Iron oxide NTs indicated a spectral sensitivity maximum at the wavelength of 500-550 nm and a long tail toward red light. These features were explained by a typical bandgap of iron oxide NTs to be ∼2.3 eV and bandgap narrowing for a small diameter NT. Organometal perovskite solar cell was constructed by using these NTs and evaluated by measuring the spectral sensitivity between the wavelength of 390 and 710 nm. For the present perovskite solar cell, drastic increase of the spectral sensitivity was obtained when we adjusted penetration depth of organometal perovskite into the porous layer of NTs. However, deep penetration worsened the spectral sensitivity. A similar trend was obtained for the cell using Zn doped iron oxide NTs, but the magnitude of incident power conversion efficiency (IPCE) became almost a half. This was explained by worsening the electrical conductivity, even the bandgap became narrower by Zn dope.