Coin Locker in JR Hiroshima Station of Shinkansen(North) exit.
There is 3 size of locker. biggest one is  W33.5 x H113.5 x D57.5 cm 700 yen for a day (Feb/2015)
This is Station map of Shinkansen exit. Info desk is available until 5:30pm.
Also another locker is in the 1F. More info in Hiroshima-Navigator web site

If you have a big suitcase or something, it is a pain to ride a local bus in the lush hour.
You can put your luggage at 88house but it cost about 560yen per person by bus returning to JR Hiroshima Sta.
Also We have a pick up service after 3pm.

広島駅新幹線口のコインロッカー情報です。
新幹線口を出て、エスカレーターを降りずに真っすぐ行きます。
一番大きいサイズのものが幅33.5センチ高さ113.5センチ奥行57.5センチで700円です。
（2015.2現在）（広島鉄道荷物　電話番号:082-261-5509）
1階もしくは他の場所にもあります。
リンクはこちらです→コインロッカーなび