A synchronization control system includes plural controlling object apparatuses connected through first and second wired OR lines. Each controlling object apparatus includes a function of switching an output to the first wired OR line from a first state to a second state in an odd numberth synchronization waiting state and switching an output to the second wired OR line from the first state to the second state in an even numberth synchronization waiting state. A control apparatus determines an odd numberth synchronization in response to changing of the first wired OR line from the first state to the second state when all the controlling object apparatuses enter the odd numberth synchronization waiting state, and determines an even numberth synchronization in response to changing of the second wired OR line from the first state to the second state when all the controlling object apparatuses enter the even numberth synchronization waiting state.