In spite of the Machiavellians' successful strategies in exploitation of others, they show cognitive deficiencies, especially reduced mind-reading skill. Theory of mind is usually regarded as an ability to make inferences about the mental states of others and thus to predict their behaviour. In our study, we have instead emphasized a motivation-based approach, using the concept of spontaneous mentalization. This concept is construed solely in a motivational context and not in relation to the automaticity of mind-reading ability. It entails that people in their social relations make efforts to explore the thoughts and intentions of others and are motivated to make hypotheses about the mental state of the other person. We assumed that what is peculiar to Machiavellianism is spontaneous mentalization as a kind of motivation rather than mind-reading as an ability. To measure spontaneous mentalization, we created a set of image stimuli and asked our participants to describe their impressions of the pictures. The results show that individual differences in spontaneous mentalization correlate positively with the scores of Machiavellianism. These results suggest that those who have a stronger motivation for putting themselves into the mind of others can be more successful in misleading and exploiting them. Further research should be carried out to clarify how spontaneous mentalization and mind-reading ability relate to each other. Copyright © 2011 John Wiley & Sons, Ltd.