Recently, Internet voting systems have gained popularity and have been used for government elections and referendums in the United Kingdom, Estonia and Switzerland as well as municipal elections in Canada and party primary elections in the United States and France. Current Internet voting systems assume either the voter's personal computer is trusted or the voter is not physically coerced. In this paper, we present an Internet voting system, in which the voter's choice remains secret even if the voter's personal computer is infected by malware or the voter is physically controlled by the adversary. In order to analyze security of our system, we give a formal definition of coercion-resistance, and provide security proof that our system is coercion-resistant. In particular, our system can achieve absolute verifiability even if all election authorities are corrupt. Based on homomorphic encryption, the overhead for tallying in our system is linear in the number of voters. Thus, our system is practical for elections at a large scale, such as general elections.