Document and Entity Information - USD ($)	12 Months Ended
	Apr. 30, 2016	Jul. 01, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	BUTLER NATIONAL CORP
Entity Central Index Key	0000015847
Current Fiscal Year End Date	--04-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Smaller Reporting Company
Entity Public Float	$ 8,046,508
Entity Common Stock, Shares Outstanding		64,066,873
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Apr. 30, 2016