A substrate includes a first region having photoelectric conversion portions and a second region having an element included in a signal processing circuit. An insulator including first and second parts respectively arranged on the first and second regions is formed on the substrate. Openings are formed in the insulator and respectively superposed on the photoelectric conversion portions. A first member is formed in the openings and on the second part of the insulator after forming the openings. At least a portion of the first member arranged on the second region is removed. The first member is planarized after removing at least the portion of the first member. A second insulator is formed on the first and second regions after planarizing the first member. A through-hole is formed in a part of the second insulator. No planarization with grinding is performed after forming the second insulator and before forming the through-hole.