A flowing water splitting apparatus splitting flowing water flowing in from a confluent pipe (14;) and conveying the water to a first pipe and a second pipe, said apparatus comprising: a first flowing water channel including a weir (24A; 24B; 24C) defining a water quantity of the flowing water flowing in from said confluent pipe and leading the flowing water flowing in from said confluent pipe to said first pipe; a second flowing water channel leading flowing water flowing over said weir (24A; 24B; 24C) to said second pipe; a plurality of partition wall portions (26A; 26B) are provided in a flow-down direction of the flowing water flowing through said first flowing water channel, to block the flowing water flowing through said first flowing water channel to form a plurality of water diversion chambers (28A; 28B; 28C) including a first water diversion chamber, a second water diversion chamber and a third water diversion chamber, partitioned in said first flowing water channel; wherein said plural water diversion chambers (28A; 28B; 28C) are successively formed along the flow-down direction of the flowing water and a flow throttle portion (30A; 30B) formed in said partition wall potions (26A; 26B) to throttle a flow quantity of the flowing water flowing from one of said water diversion chambers (28A; 28B; 28C) into another of said water diversion chambers (28A; 28B; 28C), characterized in that the weir (24A; 24B; 24C) includes a first weir portion disposed adjacent to the first water diversion chamber constituting a wall portion of the first water diversion chamber, and a second weir portion disposed adjacent to the second water diversion chamber constituting a wall portion of the second water diversion chamber, and a third weir portion adjacent to the third water diversion chamber constituting a wall portion of the third water diversion chamber,, wherein the heights of the weir portions (24A; 24B; 24C) are defined in such a way, that the first weir portion has the largest height, the second weir portion has the next largest height and the third weir portion has the smallest height. a first flowing water channel including a weir (24A; 24B; 24C) defining a water quantity of the flowing water flowing in from said confluent pipe and leading the flowing water flowing in from said confluent pipe to said first pipe; a second flowing water channel leading flowing water flowing over said weir (24A; 24B; 24C) to said second pipe; a plurality of partition wall portions (26A; 26B) are provided in a flow-down direction of the flowing water flowing through said first flowing water channel, to block the flowing water flowing through said first flowing water channel to form a plurality of water diversion chambers (28A; 28B; 28C) including a first water diversion chamber, a second water diversion chamber and a third water diversion chamber, partitioned in said first flowing water channel; wherein said plural water diversion chambers (28A; 28B; 28C) are successively formed along the flow-down direction of the flowing water and a flow throttle portion (30A; 30B) formed in said partition wall potions (26A; 26B) to throttle a flow quantity of the flowing water flowing from one of said water diversion chambers (28A; 28B; 28C) into another of said water diversion chambers (28A; 28B; 28C), characterized in that the weir (24A; 24B; 24C) includes a first weir portion disposed adjacent to the first water diversion chamber constituting a wall portion of the first water diversion chamber, and a second weir portion disposed adjacent to the second water diversion chamber constituting a wall portion of the second water diversion chamber, and a third weir portion adjacent to the third water diversion chamber constituting a wall portion of the third water diversion chamber,, wherein the heights of the weir portions (24A; 24B; 24C) are defined in such a way, that the first weir portion has the largest height, the second weir portion has the next largest height and the third weir portion has the smallest height.