Note 8 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets, Valuation Allowance, Total	$ 5,285,222	$ 5,422,433
LiqTech International Inc and LiqTech NA [Member]
Deferred Tax Assets, Valuation Allowance, Total	3,845,000	3,428,000
LiqTech International AS and LiqTech Systems AS [Member]
Deferred Tax Assets, Valuation Allowance, Total	1,209,000	1,846,000
LiqTech Germany [Member]
Deferred Tax Assets, Valuation Allowance, Total	129,000	132,000
LiqTech Singapore [Member]
Deferred Tax Assets, Valuation Allowance, Total	102,000	105,000
Internal Revenue Service (IRS) [Member] | Domestic Tax Authority [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	19,258,541
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	416,000	460,000
Danish Ministry of Taxation [Member] | Foreign Tax Authority [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	8,228,823
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(637,000)	42,000
Federal Ministry of Finance, Germany [Member] | Foreign Tax Authority [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	464,022
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(3,000)	(7,000)
Inland Revenue, Singapore (IRAS) [Member] | Foreign Tax Authority [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	602,887
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ (2,000)	$ (5,000)