Coalescence of two planar air bubbles in stagnant water filled in two parallel plates was experimentally investigated. To examine the effects of bubble wake on coalescence, the bubble diameter, initial vertical and horizontal distances between two bubbles were chosen as experimental parameters. The vertical distance x from the bubble release point, at which coalescence took place, was measured. The number of coalesced bubble pairs was counted for about 100 bubble pairs, and the coalescence probability was calculated as the ratio of the number of the coalesced bubble pairs to that of the total bubble pairs. With decreasing the bubble diameter or with increasing the initial distance between two bubbles, the mean vertical distance x increased and the coalescence probability decreased. There was a strong correlation between the distribution of coalescence probability and that of bubble wake velocity, i.e. the wake structure does play a significant role in the bubble coalescence process and affects the coalescence probability.