Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	EVOK
Entity Registrant Name	Evoke Pharma Inc
Entity Central Index Key	0001403708
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-36075
Entity Tax Identification Number	20-8447886
Entity Address, Address Line One	420 Stevens Avenue
Entity Address, Address Line Two	Suite 370
Entity Address, City or Town	Solana Beach
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92075
City Area Code	858
Local Phone Number	345-1494
Entity Incorporation, State or Country Code	DE
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		32,656,480
Document Quarterly Report	true
Document Transition Report	false