| Document And Entity Information | Oct. 18, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | BUTLER NATIONAL CORPORATION |
| Document, Type | 8-K |
| Document, Period End Date | Oct. 18, 2021 |
| Entity, Incorporation, State or Country Code | KS |
| Entity, File Number | 0-1678 |
| Entity, Tax Identification Number | 41-0834293 |
| Entity, Address, Address Line One | 19920 W. 161st Street |
| Entity, Address, City or Town | Olathe |
| Entity, Address, State or Province | KS |
| Entity, Address, Postal Zip Code | 66062 |
| City Area Code | 913 |
| Local Phone Number | 780-9595 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000015847 |
