Document And Entity Information (USD $)	6 Months Ended
	Oct. 31, 2011	Dec. 02, 2011	Jul. 22, 2011
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	Non-accelerated Filer
Entity Public Float			$ 30,312,811
Entity Common Stock, Shares Outstanding		57,194,262
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Oct. 31, 2011