Cover Page - shares	6 Months Ended
	Jun. 30, 2023	Aug. 04, 2023
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Registrant Name	Apexigen, Inc.
Entity Central Index Key	0001814140
Entity File Number	001-39488
Entity Tax Identification Number	85-1260244
Current Fiscal Year End Date	--12-31
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Address, Address Line One	900 Industrial Road
Entity Address, Address Line Two	Suite C
Entity Address, City or Town	San Carlos
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94070
Entity Incorporation, State or Country Code	DE
City Area Code	650
Local Phone Number	931-6236
Entity Common Stock, Shares Outstanding		24,861,926
Common Stock [Member]
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	APGN
Security Exchange Name	NASDAQ
Warrants [Member]
Document Information [Line Items]
Title of 12(b) Security	Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $11.50 per share
Trading Symbol	APGNW
Security Exchange Name	NASDAQ