Objective: The aim of this research was to assess gaze behaviors and facial affect expressions in mother-infant interaction within the frame of self-contingency and interactive contingency, reflecting self-regulation and interactive regulation, respectively. In Model 1, second-by-second changing gaze behaviors (on partner's face/off partner's face) and in Model 2, facial affect expressions (from positive to negative) were examined. Self-contingency reflects the variability or stability in gaze directions and facial affect expressions in each partner. Interactive contingency reflects the degree of mother-infant gaze and facial affect attunement or interactive regulation relative to each other. Method: Sample was composed of 56 healthy mother-infant dyads. All infants were 4 months old, and mean maternal age was 29.61 (SD=3.71). Mother-infant interactions were filmed at the lab. Interactions were coded second-by-second for mother-infant gaze behaviors and facial affect expressions with video microanalysis method. The analysis method was multilevel-multivariate time series analysis. Results: According to Model 1-2, mother-infant gaze behaviors and facial affect expressions were neither too stable nor too variable, rather, the change in gaze behaviors and facial affect expressions in each partner showed predictable patterns. Mothers regulated their gaze behaviors and facial affect expressions in relation to that of their infants. Infants regulated their facial affect expressions in relation to their mothers' facial affect expressions, but infant gaze interactive contingency to mother gaze was marginally significant. Conclusion: In interactions, infants and mothers regulate the rhythms of their own behavior and at the same time contingently coordinate with that of the partner. This bi-directionally regulating environment is the foundation of infants' relationship expectations and bio-social-behavioral regulation capacity, which may be related to psychopathology in future.