1. If a Muslim who has reached puberty laughs laud enough for a second person to hear in a salah that consists of ruku' and sujood, not only will his Wuzu be nullified but so will his salah.If he laughs only loud enough for himself to hear, his salah will be invalidated but not his Wuzu. Smiling ( Without creating a sound ) invalidates neither the Wuzu nor the salah. ( Maraqil falah ma ; Hashiya-tut-tahtawi, P91)
2. If a Muslim of the same age category laughs loudly in a funeral prayer, his salah will become invalid but not his Wuzu.( ibid )
3. Laughing other then in salah does not invalidate Wuzu but to repeat it is preferable.( Maraqil falah ma' Hashiya-tut-tahtawi, P84 )

Hadith :

Our Holy Prophet ( p.b.u.h ) never laughed loudly so we should attmpt to revive this blessed sunnah and avoid laughing out aloud. Our Holy Propet (p.b.u.h ) has said : Smiling is from Allah (Azza Wajal) and laughing is from the devil . ( Al Mu'jamus Saghir Littabarani, Juz 2 , P104, Dar-ul-Kutubul Ilmiyyah Beirut )