This study looks into the Theory of Mind (ToM) development of autistic children in Macau. Wellman and Liu’s (2004) Theory of Mind Tasks is used to examine the development of ToM ability among autistic children, and to compare it with that of Down’s syndrome and normal children. The sample includes 16 autistic, 12 Down’s syndrome and 104 normal children, a total of 132. Two sub-samples are drawn, which aim to compare autistic children with the other two groups of a similar age and verbal age in terms of PPVT score. The psychometric properties of Wellman’s scale are investigated in detail. As the sample of autistic children is relatively small, both parametric and non-parametric statistical procedures are used. Results showed that the ToM ability of autistic children was significantly lower than that of Down’s syndrome or normal children of a similar age and verbal age. But their ToM ability does not vanish, which leads to the conjecture that they can be gradually developed. Though Pearson correlations are non-significant, the effect sizes of ToM ability against age and verbal age are respectively medium and large in the case of autistic children, whose development is at least five years later than normal. There are potential correlations between ToM ability with verbal age.