PURPOSE: To provide the panning effect generating device which represents a stereophonic musical sound with a rich dynamic feeling and a live feeling by varying the right and left distribution of the sound corresponding to the strength and position of keying or at random each time a key of an electronic musical instrument is pressed.

CONSTITUTION: This panning effect generating device consists of a velocity generating means 11, a key scaling generating means 12, a parameter storage means 3 storing with parameters prescribing the extent of panning effect according to information generated by the velocity generating means 11 and key scaling generating means 12, and a panning effect control means 2 which determines a panning execution value according to parameters read out of the parameter storage means 3. Further, the device is provided with a random data generating means 1 which generates random data and a panning effect control means 2 which determines the panning execution value for generating panning effect on the basis of the random data generated by the random data generating means 1.