This paper proposes a secure protocol for web-based questionnaire that preserves the privacy of responders and ensures the robustness. The proposed protocol is based on secure electronic voting protocol proposed by Cramer et al. confidentiality and efficiency, which are common requirements for both applications. This paper points out an issue particular in the secure questionnaire, that is, a requirement to deal with a multiple-choice question, and shows that the communication overhead grows exponentially with the number of choices n. To address the issue, the proposed protocol reduces the cost from Θ(2^n) to Θ(n). The performance based on the experimental implementation is also shown.