Manjurul Islam, an MP for the governing Awami League, was shot several times by three men in Gaibandha district, police say.
He later died in hospital and the identities of his assailants, who reportedly fled by motorbike, remain unknown.
Protests have been held in the local area following the killing.
Prof Bimal Chandra Roy of Rangpur Medical College Hospital told BBC Bengali that the MP had been shot five times, likely from close range.
Mr Islam was arrested in October 2015 for allegedly shooting a schoolboy but was later released on bail.