Examining cortical folding development at various scales may help better understand brain cognition and motor functions. We propose a curvature-based multi-scale method using spherical wavelets to study the longitudinal changes of cortical folding during infancy. We applied our method on 219 longitudinal MR images from 73 healthy infants at 0, 1, and 2 years of age. We reveal scale-specific and region-specific developmental patterns of infant cortical folding. Specifically, at coarser levels, many primary folds flatten out; while at finer levels, the majority of the minor folds become more convoluted, providing new insights into early brain development.