Johnny's Jimunsho is not inclueded because they have a different financial reporting period. They would probably be the No. 1 otherwise. Names in brackets are the main artistes they manage.
1) Avex (Hamasaki Ayumi, Koda Kumi)
2) Upfront (Morning Musume, Matsuura Aya)
3) Yoshimoto Kogyo (Akashiya Sanma, Downtown)
4) Watanabe Entertainment (Neptune, Aoki Sayaka)
5) Furutachi Project (Furutachi Ichiro)
6) Horipro (Wada Akiko, Tsumabuki Satoshi)
7) Toriryuusha (Mr.Children, Remioromen)
8) Amuse (Southern All Stars, Fukuyama Masaharu)
9) Ken-On (Hirai Ken, Ito Misaki, Amami Yuki)
10) Rising Pro (Amuro Namie, Kuninaka Ryoko)
Source: Dorama World
Original source:
http://kireaji.net/blog/2006/07/shotoku030706